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Fred Drake 1998-03-10 05:20:33 +00:00
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169
Doc/lib/libsocket.tex
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@ -1,7 +1,7 @@
\section{Built-in Module \sectcode{socket}} \section{Built-in Module \sectcode{socket}}
\label{module-socket} \label{module-socket}
\bimodindex{socket} \bimodindex{socket}
This module provides access to the BSD \emph{socket} interface. This module provides access to the BSD \emph{socket} interface.
It is available on \UNIX{} systems that support this interface. It is available on \UNIX{} systems that support this interface.
@ -16,17 +16,17 @@ socket semantics.
The Python interface is a straightforward transliteration of the The Python interface is a straightforward transliteration of the
\UNIX{} system call and library interface for sockets to Python's \UNIX{} system call and library interface for sockets to Python's
object-oriented style: the \code{socket()} function returns a object-oriented style: the \function{socket()} function returns a
\dfn{socket object} whose methods implement the various socket system \dfn{socket object} whose methods implement the various socket system
calls. Parameter types are somewhat higher-level than in the C calls. Parameter types are somewhat higher-level than in the C
interface: as with \code{read()} and \code{write()} operations on Python interface: as with \method{read()} and \method{write()} operations on
files, buffer allocation on receive operations is automatic, and Python files, buffer allocation on receive operations is automatic,
buffer length is implicit on send operations. and buffer length is implicit on send operations.
Socket addresses are represented as a single string for the Socket addresses are represented as a single string for the
\code{AF_UNIX} address family and as a pair \constant{AF_UNIX} address family and as a pair
\code{(\var{host}, \var{port})} for the \code{AF_INET} address family, \code{(\var{host}, \var{port})} for the \constant{AF_INET} address
where \var{host} is a string representing family, where \var{host} is a string representing
either a hostname in Internet domain notation like either a hostname in Internet domain notation like
\code{'daring.cwi.nl'} or an IP address like \code{'100.50.200.5'}, \code{'daring.cwi.nl'} or an IP address like \code{'100.50.200.5'},
and \var{port} is an integral port number. Other address families are and \var{port} is an integral port number. Other address families are
@ -35,8 +35,8 @@ socket object is automatically selected based on the address family
specified when the socket object was created. specified when the socket object was created.
For IP addresses, two special forms are accepted instead of a host For IP addresses, two special forms are accepted instead of a host
address: the empty string represents \code{INADDR_ANY}, and the string address: the empty string represents \constant{INADDR_ANY}, and the string
\code{"<broadcast>"} represents \code{INADDR_BROADCAST}. \code{"<broadcast>"} represents \constant{INADDR_BROADCAST}.
All errors raise exceptions. The normal exceptions for invalid All errors raise exceptions. The normal exceptions for invalid
argument types and out-of-memory conditions can be raised; errors argument types and out-of-memory conditions can be raised; errors
@ -45,9 +45,9 @@ related to socket or address semantics raise the error \code{socket.error}.
Non-blocking mode is supported through the \code{setblocking()} Non-blocking mode is supported through the \code{setblocking()}
method. method.
The module \code{socket} exports the following constants and functions: The module \module{socket} exports the following constants and functions:
\setindexsubitem{(in module socket)}
\begin{excdesc}{error} \begin{excdesc}{error}
This exception is raised for socket- or address-related errors. This exception is raised for socket- or address-related errors.
The accompanying value is either a string telling what went wrong or a The accompanying value is either a string telling what went wrong or a
@ -61,8 +61,9 @@ names for the error codes defined by the underlying operating system.
\begin{datadesc}{AF_UNIX} \begin{datadesc}{AF_UNIX}
\dataline{AF_INET} \dataline{AF_INET}
These constants represent the address (and protocol) families, These constants represent the address (and protocol) families,
used for the first argument to \code{socket()}. If the \code{AF_UNIX} used for the first argument to \function{socket()}. If the
constant is not defined then this protocol is unsupported. \constant{AF_UNIX} constant is not defined then this protocol is
unsupported.
\end{datadesc} \end{datadesc}
\begin{datadesc}{SOCK_STREAM} \begin{datadesc}{SOCK_STREAM}
@ -71,9 +72,9 @@ constant is not defined then this protocol is unsupported.
\dataline{SOCK_RDM} \dataline{SOCK_RDM}
\dataline{SOCK_SEQPACKET} \dataline{SOCK_SEQPACKET}
These constants represent the socket types, These constants represent the socket types,
used for the second argument to \code{socket()}. used for the second argument to \function{socket()}.
(Only \code{SOCK_STREAM} and (Only \constant{SOCK_STREAM} and
\code{SOCK_DGRAM} appear to be generally useful.) \constant{SOCK_DGRAM} appear to be generally useful.)
\end{datadesc} \end{datadesc}
\begin{datadesc}{SO_*} \begin{datadesc}{SO_*}
@ -86,8 +87,8 @@ used for the second argument to \code{socket()}.
\dataline{IP_*} \dataline{IP_*}
Many constants of these forms, documented in the \UNIX{} documentation on Many constants of these forms, documented in the \UNIX{} documentation on
sockets and/or the IP protocol, are also defined in the socket module. sockets and/or the IP protocol, are also defined in the socket module.
They are generally used in arguments to the \code{setsockopt} and They are generally used in arguments to the \method{setsockopt()} and
\code{getsockopt} methods of socket objects. In most cases, only \method{getsockopt()} methods of socket objects. In most cases, only
those symbols that are defined in the \UNIX{} header files are defined; those symbols that are defined in the \UNIX{} header files are defined;
for a few symbols, default values are provided. for a few symbols, default values are provided.
\end{datadesc} \end{datadesc}
@ -101,20 +102,19 @@ is an IP address itself it is returned unchanged.
\begin{funcdesc}{gethostname}{} \begin{funcdesc}{gethostname}{}
Return a string containing the hostname of the machine where Return a string containing the hostname of the machine where
the Python interpreter is currently executing. If you want to know the the Python interpreter is currently executing. If you want to know the
current machine's IP address, use current machine's IP address, use \code{gethostbyname(gethostname())}.
\code{socket.gethostbyname(socket.gethostname())}. Note: \function{gethostname()} doesn't always return the fully qualified
Note: \code{gethostname()} doesn't always return the fully qualified domain name; use \code{gethostbyaddr(gethostname())}
domain name; use \code{socket.gethostbyaddr(socket.gethostname())}
(see below). (see below).
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{gethostbyaddr}{ip_address} \begin{funcdesc}{gethostbyaddr}{ip_address}
Return a triple \code{(hostname, aliaslist, ipaddrlist)} where Return a triple \code{(\var{hostname}, \var{aliaslist},
\code{hostname} is the primary host name responding to the given \var{ipaddrlist})} where \var{hostname} is the primary host name
\var{ip_address}, \code{aliaslist} is a (possibly empty) list of responding to the given \var{ip_address}, \var{aliaslist} is a
alternative host names for the same address, and \code{ipaddrlist} is (possibly empty) list of alternative host names for the same address,
a list of IP addresses for the same interface on the same and \var{ipaddrlist} is a list of IP addresses for the same interface
host (most likely containing only a single address). on the same host (most likely containing only a single address).
To find the fully qualified domain name, check \var{hostname} and the To find the fully qualified domain name, check \var{hostname} and the
items of \var{aliaslist} for an entry containing at least one period. items of \var{aliaslist} for an entry containing at least one period.
\end{funcdesc} \end{funcdesc}
@ -122,29 +122,29 @@ items of \var{aliaslist} for an entry containing at least one period.
\begin{funcdesc}{getprotobyname}{protocolname} \begin{funcdesc}{getprotobyname}{protocolname}
Translate an Internet protocol name (e.g. \code{'icmp'}) to a constant Translate an Internet protocol name (e.g. \code{'icmp'}) to a constant
suitable for passing as the (optional) third argument to the suitable for passing as the (optional) third argument to the
\code{socket()} function. This is usually only needed for sockets \function{socket()} function. This is usually only needed for sockets
opened in ``raw'' mode (\code{SOCK_RAW}); for the normal socket modes, opened in ``raw'' mode (\constant{SOCK_RAW}); for the normal socket
the correct protocol is chosen automatically if the protocol is modes, the correct protocol is chosen automatically if the protocol is
omitted or zero. omitted or zero.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getservbyname}{servicename\, protocolname} \begin{funcdesc}{getservbyname}{servicename, protocolname}
Translate an Internet service name and protocol name to a port number Translate an Internet service name and protocol name to a port number
for that service. The protocol name should be \code{'tcp'} or for that service. The protocol name should be \code{'tcp'} or
\code{'udp'}. \code{'udp'}.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{socket}{family\, type\optional{\, proto}} \begin{funcdesc}{socket}{family, type\optional{, proto}}
Create a new socket using the given address family, socket type and Create a new socket using the given address family, socket type and
protocol number. The address family should be \code{AF_INET} or protocol number. The address family should be \constant{AF_INET} or
\code{AF_UNIX}. The socket type should be \code{SOCK_STREAM}, \constant{AF_UNIX}. The socket type should be \constant{SOCK_STREAM},
\code{SOCK_DGRAM} or perhaps one of the other \samp{SOCK_} constants. \constant{SOCK_DGRAM} or perhaps one of the other \samp{SOCK_} constants.
The protocol number is usually zero and may be omitted in that case. The protocol number is usually zero and may be omitted in that case.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{fromfd}{fd\, family\, type\optional{\, proto}} \begin{funcdesc}{fromfd}{fd, family, type\optional{, proto}}
Build a socket object from an existing file descriptor (an integer as Build a socket object from an existing file descriptor (an integer as
returned by a file object's \code{fileno} method). Address family, returned by a file object's \method{fileno()} method). Address family,
socket type and protocol number are as for the \code{socket} function socket type and protocol number are as for the \code{socket} function
above. The file descriptor should refer to a socket, but this is not above. The file descriptor should refer to a socket, but this is not
checked --- subsequent operations on the object may fail if the file checked --- subsequent operations on the object may fail if the file
@ -180,15 +180,14 @@ no-op; otherwise, it performs a 2-byte swap operation.
\begin{datadesc}{SocketType} \begin{datadesc}{SocketType}
This is a Python type object that represents the socket object type. This is a Python type object that represents the socket object type.
It is the same as \code{type(socket.socket(...))}. It is the same as \code{type(socket(...))}.
\end{datadesc} \end{datadesc}
\subsection{Socket Objects} \subsection{Socket Objects}
\noindent
Socket objects have the following methods. Except for Socket objects have the following methods. Except for
\code{makefile()} these correspond to \UNIX{} system calls applicable to \method{makefile()} these correspond to \UNIX{} system calls
sockets. applicable to sockets.
\setindexsubitem{(socket method)} \setindexsubitem{(socket method)}
\begin{funcdesc}{accept}{} \begin{funcdesc}{accept}{}
@ -213,19 +212,20 @@ Sockets are automatically closed when they are garbage-collected.
\begin{funcdesc}{connect}{address} \begin{funcdesc}{connect}{address}
Connect to a remote socket at \var{address}. Connect to a remote socket at \var{address}.
(The format of \var{address} depends on the address family --- see above.) (The format of \var{address} depends on the address family --- see
above.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{connect_ex}{address} \begin{funcdesc}{connect_ex}{address}
Like \code{connect(\var{address})}, but return an error indicator Like \code{connect(\var{address})}, but return an error indicator
instead of raising an exception. The error indicator is 0 if the instead of raising an exception. The error indicator is 0 if the
operation succeeded, otherwise the value of the \code{errno} operation succeeded, otherwise the value of the \cdata{errno}
variable. This is useful e.g. for asynchronous connects. variable. This is useful e.g. for asynchronous connects.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{fileno}{} \begin{funcdesc}{fileno}{}
Return the socket's file descriptor (a small integer). This is useful Return the socket's file descriptor (a small integer). This is useful
with \code{select}. with \function{select.select()}.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getpeername}{} \begin{funcdesc}{getpeername}{}
@ -242,16 +242,16 @@ number of an IP socket, for instance.
see above.) see above.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getsockopt}{level\, optname\optional{\, buflen}} \begin{funcdesc}{getsockopt}{level, optname\optional{, buflen}}
Return the value of the given socket option (see the \UNIX{} man page Return the value of the given socket option (see the \UNIX{} man page
\emph{getsockopt}(2)). The needed symbolic constants (\code{SO_*} etc.) \manpage{getsockopt}{2}). The needed symbolic constants
are defined in this module. If \var{buflen} (\constant{SO_*} etc.) are defined in this module. If \var{buflen}
is absent, an integer option is assumed and its integer value is absent, an integer option is assumed and its integer value
is returned by the function. If \var{buflen} is present, it specifies is returned by the function. If \var{buflen} is present, it specifies
the maximum length of the buffer used to receive the option in, and the maximum length of the buffer used to receive the option in, and
this buffer is returned as a string. It is up to the caller to decode this buffer is returned as a string. It is up to the caller to decode
the contents of the buffer (see the optional built-in module the contents of the buffer (see the optional built-in module
\code{struct} for a way to decode C structures encoded as strings). \module{struct} for a way to decode C structures encoded as strings).
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{listen}{backlog} \begin{funcdesc}{listen}{backlog}
@ -262,42 +262,42 @@ least 1; the maximum value is system-dependent (usually 5).
\begin{funcdesc}{makefile}{\optional{mode\optional{\, bufsize}}} \begin{funcdesc}{makefile}{\optional{mode\optional{\, bufsize}}}
Return a \dfn{file object} associated with the socket. (File objects Return a \dfn{file object} associated with the socket. (File objects
were described earlier under Built-in Types.) The file object were described earlier in \ref{bltin-file-objects}, ``File Objects.'')
references a \code{dup()}ped version of the socket file descriptor, so The file object references a \cfunction{dup()}ped version of the
the file object and socket object may be closed or garbage-collected socket file descriptor, so the file object and socket object may be
independently. The optional \var{mode} and \var{bufsize} arguments closed or garbage-collected independently. The optional \var{mode}
are interpreted the same way as by the built-in and \var{bufsize} arguments are interpreted the same way as by the
\code{open()} function. built-in \function{open()} function.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{recv}{bufsize\optional{\, flags}} \begin{funcdesc}{recv}{bufsize\optional{, flags}}
Receive data from the socket. The return value is a string representing Receive data from the socket. The return value is a string representing
the data received. The maximum amount of data to be received the data received. The maximum amount of data to be received
at once is specified by \var{bufsize}. See the \UNIX{} manual page at once is specified by \var{bufsize}. See the \UNIX{} manual page
for the meaning of the optional argument \var{flags}; it defaults to \manpage{recv}{2} for the meaning of the optional argument
zero. \var{flags}; it defaults to zero.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{recvfrom}{bufsize\optional{\, flags}} \begin{funcdesc}{recvfrom}{bufsize\optional{, flags}}
Receive data from the socket. The return value is a pair Receive data from the socket. The return value is a pair
\code{(\var{string}, \var{address})} where \var{string} is a string \code{(\var{string}, \var{address})} where \var{string} is a string
representing the data received and \var{address} is the address of the representing the data received and \var{address} is the address of the
socket sending the data. The optional \var{flags} argument has the socket sending the data. The optional \var{flags} argument has the
same meaning as for \code{recv()} above. same meaning as for \method{recv()} above.
(The format of \var{address} depends on the address family --- see above.) (The format of \var{address} depends on the address family --- see above.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{send}{string\optional{\, flags}} \begin{funcdesc}{send}{string\optional{, flags}}
Send data to the socket. The socket must be connected to a remote Send data to the socket. The socket must be connected to a remote
socket. The optional \var{flags} argument has the same meaning as for socket. The optional \var{flags} argument has the same meaning as for
\code{recv()} above. Return the number of bytes sent. \method{recv()} above. Returns the number of bytes sent.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{sendto}{string\optional{\, flags}\, address} \begin{funcdesc}{sendto}{string\optional{\, flags}\, address}
Send data to the socket. The socket should not be connected to a Send data to the socket. The socket should not be connected to a
remote socket, since the destination socket is specified by remote socket, since the destination socket is specified by
\code{address}. The optional \var{flags} argument has the same \var{address}. The optional \var{flags} argument has the same
meaning as for \code{recv()} above. Return the number of bytes sent. meaning as for \method{recv()} above. Return the number of bytes sent.
(The format of \var{address} depends on the address family --- see above.) (The format of \var{address} depends on the address family --- see above.)
\end{funcdesc} \end{funcdesc}
@ -305,30 +305,32 @@ meaning as for \code{recv()} above. Return the number of bytes sent.
Set blocking or non-blocking mode of the socket: if \var{flag} is 0, Set blocking or non-blocking mode of the socket: if \var{flag} is 0,
the socket is set to non-blocking, else to blocking mode. Initially the socket is set to non-blocking, else to blocking mode. Initially
all sockets are in blocking mode. In non-blocking mode, if a all sockets are in blocking mode. In non-blocking mode, if a
\code{recv} call doesn't find any data, or if a \code{send} call can't \method{recv()} call doesn't find any data, or if a \code{send} call can't
immediately dispose of the data, a \code{socket.error} exception is immediately dispose of the data, a \exception{error} exception is
raised; in blocking mode, the calls block until they can proceed. raised; in blocking mode, the calls block until they can proceed.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{setsockopt}{level\, optname\, value} \begin{funcdesc}{setsockopt}{level\, optname\, value}
Set the value of the given socket option (see the \UNIX{} man page Set the value of the given socket option (see the \UNIX{} man page
\emph{setsockopt}(2)). The needed symbolic constants are defined in \manpage{setsockopt}{2}). The needed symbolic constants are defined in
the \code{socket} module (\code{SO_*} etc.). The value can be an the \module{socket} module (\code{SO_*} etc.). The value can be an
integer or a string representing a buffer. In the latter case it is integer or a string representing a buffer. In the latter case it is
up to the caller to ensure that the string contains the proper bits up to the caller to ensure that the string contains the proper bits
(see the optional built-in module (see the optional built-in module
\code{struct} for a way to encode C structures as strings). \module{struct}\refbimodindex{struct} for a way to encode C structures
as strings).
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{shutdown}{how} \begin{funcdesc}{shutdown}{how}
Shut down one or both halves of the connection. If \var{how} is \code{0}, Shut down one or both halves of the connection. If \var{how} is
further receives are disallowed. If \var{how} is \code{1}, further sends are \code{0}, further receives are disallowed. If \var{how} is \code{1},
disallowed. If \var{how} is \code{2}, further sends and receives are further sends are disallowed. If \var{how} is \code{2}, further sends
disallowed. and receives are disallowed.
\end{funcdesc} \end{funcdesc}
Note that there are no methods \code{read()} or \code{write()}; use Note that there are no methods \method{read()} or \method{write()};
\code{recv()} and \code{send()} without \var{flags} argument instead. use \method{recv()} and \method{send()} without \var{flags} argument
instead.
\subsection{Example} \subsection{Example}
\nodename{Socket Example} \nodename{Socket Example}
@ -336,12 +338,13 @@ Note that there are no methods \code{read()} or \code{write()}; use
Here are two minimal example programs using the TCP/IP protocol:\ a Here are two minimal example programs using the TCP/IP protocol:\ a
server that echoes all data that it receives back (servicing only one server that echoes all data that it receives back (servicing only one
client), and a client using it. Note that a server must perform the client), and a client using it. Note that a server must perform the
sequence \code{socket}, \code{bind}, \code{listen}, \code{accept} sequence \function{socket()}, \method{bind()}, \method{listen()},
(possibly repeating the \code{accept} to service more than one client), \method{accept()} (possibly repeating the \method{accept()} to service
while a client only needs the sequence \code{socket}, \code{connect}. more than one client), while a client only needs the sequence
Also note that the server does not \code{send}/\code{receive} on the \function{socket()}, \method{connect()}. Also note that the server
does not \method{send()}/\method{recv()} on the
socket it is listening on but on the new socket returned by socket it is listening on but on the new socket returned by
\code{accept}. \method{accept()}.
\begin{verbatim} \begin{verbatim}
# Echo server program # Echo server program
@ -359,7 +362,7 @@ while 1:
conn.send(data) conn.send(data)
conn.close() conn.close()
\end{verbatim} \end{verbatim}
%
\begin{verbatim} \begin{verbatim}
# Echo client program # Echo client program
from socket import * from socket import *
@ -372,7 +375,7 @@ data = s.recv(1024)
s.close() s.close()
print 'Received', `data` print 'Received', `data`
\end{verbatim} \end{verbatim}
%
\begin{seealso} \begin{seealso}
\seemodule{SocketServer}{classes that simplify writing network servers} \seemodule{SocketServer}{classes that simplify writing network servers}
\end{seealso} \end{seealso}

169
Doc/libsocket.tex
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@ -1,7 +1,7 @@
\section{Built-in Module \sectcode{socket}} \section{Built-in Module \sectcode{socket}}
\label{module-socket} \label{module-socket}
\bimodindex{socket} \bimodindex{socket}
This module provides access to the BSD \emph{socket} interface. This module provides access to the BSD \emph{socket} interface.
It is available on \UNIX{} systems that support this interface. It is available on \UNIX{} systems that support this interface.
@ -16,17 +16,17 @@ socket semantics.
The Python interface is a straightforward transliteration of the The Python interface is a straightforward transliteration of the
\UNIX{} system call and library interface for sockets to Python's \UNIX{} system call and library interface for sockets to Python's
object-oriented style: the \code{socket()} function returns a object-oriented style: the \function{socket()} function returns a
\dfn{socket object} whose methods implement the various socket system \dfn{socket object} whose methods implement the various socket system
calls. Parameter types are somewhat higher-level than in the C calls. Parameter types are somewhat higher-level than in the C
interface: as with \code{read()} and \code{write()} operations on Python interface: as with \method{read()} and \method{write()} operations on
files, buffer allocation on receive operations is automatic, and Python files, buffer allocation on receive operations is automatic,
buffer length is implicit on send operations. and buffer length is implicit on send operations.
Socket addresses are represented as a single string for the Socket addresses are represented as a single string for the
\code{AF_UNIX} address family and as a pair \constant{AF_UNIX} address family and as a pair
\code{(\var{host}, \var{port})} for the \code{AF_INET} address family, \code{(\var{host}, \var{port})} for the \constant{AF_INET} address
where \var{host} is a string representing family, where \var{host} is a string representing
either a hostname in Internet domain notation like either a hostname in Internet domain notation like
\code{'daring.cwi.nl'} or an IP address like \code{'100.50.200.5'}, \code{'daring.cwi.nl'} or an IP address like \code{'100.50.200.5'},
and \var{port} is an integral port number. Other address families are and \var{port} is an integral port number. Other address families are
@ -35,8 +35,8 @@ socket object is automatically selected based on the address family
specified when the socket object was created. specified when the socket object was created.
For IP addresses, two special forms are accepted instead of a host For IP addresses, two special forms are accepted instead of a host
address: the empty string represents \code{INADDR_ANY}, and the string address: the empty string represents \constant{INADDR_ANY}, and the string
\code{"<broadcast>"} represents \code{INADDR_BROADCAST}. \code{"<broadcast>"} represents \constant{INADDR_BROADCAST}.
All errors raise exceptions. The normal exceptions for invalid All errors raise exceptions. The normal exceptions for invalid
argument types and out-of-memory conditions can be raised; errors argument types and out-of-memory conditions can be raised; errors
@ -45,9 +45,9 @@ related to socket or address semantics raise the error \code{socket.error}.
Non-blocking mode is supported through the \code{setblocking()} Non-blocking mode is supported through the \code{setblocking()}
method. method.
The module \code{socket} exports the following constants and functions: The module \module{socket} exports the following constants and functions:
\setindexsubitem{(in module socket)}
\begin{excdesc}{error} \begin{excdesc}{error}
This exception is raised for socket- or address-related errors. This exception is raised for socket- or address-related errors.
The accompanying value is either a string telling what went wrong or a The accompanying value is either a string telling what went wrong or a
@ -61,8 +61,9 @@ names for the error codes defined by the underlying operating system.
\begin{datadesc}{AF_UNIX} \begin{datadesc}{AF_UNIX}
\dataline{AF_INET} \dataline{AF_INET}
These constants represent the address (and protocol) families, These constants represent the address (and protocol) families,
used for the first argument to \code{socket()}. If the \code{AF_UNIX} used for the first argument to \function{socket()}. If the
constant is not defined then this protocol is unsupported. \constant{AF_UNIX} constant is not defined then this protocol is
unsupported.
\end{datadesc} \end{datadesc}
\begin{datadesc}{SOCK_STREAM} \begin{datadesc}{SOCK_STREAM}
@ -71,9 +72,9 @@ constant is not defined then this protocol is unsupported.
\dataline{SOCK_RDM} \dataline{SOCK_RDM}
\dataline{SOCK_SEQPACKET} \dataline{SOCK_SEQPACKET}
These constants represent the socket types, These constants represent the socket types,
used for the second argument to \code{socket()}. used for the second argument to \function{socket()}.
(Only \code{SOCK_STREAM} and (Only \constant{SOCK_STREAM} and
\code{SOCK_DGRAM} appear to be generally useful.) \constant{SOCK_DGRAM} appear to be generally useful.)
\end{datadesc} \end{datadesc}
\begin{datadesc}{SO_*} \begin{datadesc}{SO_*}
@ -86,8 +87,8 @@ used for the second argument to \code{socket()}.
\dataline{IP_*} \dataline{IP_*}
Many constants of these forms, documented in the \UNIX{} documentation on Many constants of these forms, documented in the \UNIX{} documentation on
sockets and/or the IP protocol, are also defined in the socket module. sockets and/or the IP protocol, are also defined in the socket module.
They are generally used in arguments to the \code{setsockopt} and They are generally used in arguments to the \method{setsockopt()} and
\code{getsockopt} methods of socket objects. In most cases, only \method{getsockopt()} methods of socket objects. In most cases, only
those symbols that are defined in the \UNIX{} header files are defined; those symbols that are defined in the \UNIX{} header files are defined;
for a few symbols, default values are provided. for a few symbols, default values are provided.
\end{datadesc} \end{datadesc}
@ -101,20 +102,19 @@ is an IP address itself it is returned unchanged.
\begin{funcdesc}{gethostname}{} \begin{funcdesc}{gethostname}{}
Return a string containing the hostname of the machine where Return a string containing the hostname of the machine where
the Python interpreter is currently executing. If you want to know the the Python interpreter is currently executing. If you want to know the
current machine's IP address, use current machine's IP address, use \code{gethostbyname(gethostname())}.
\code{socket.gethostbyname(socket.gethostname())}. Note: \function{gethostname()} doesn't always return the fully qualified
Note: \code{gethostname()} doesn't always return the fully qualified domain name; use \code{gethostbyaddr(gethostname())}
domain name; use \code{socket.gethostbyaddr(socket.gethostname())}
(see below). (see below).
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{gethostbyaddr}{ip_address} \begin{funcdesc}{gethostbyaddr}{ip_address}
Return a triple \code{(hostname, aliaslist, ipaddrlist)} where Return a triple \code{(\var{hostname}, \var{aliaslist},
\code{hostname} is the primary host name responding to the given \var{ipaddrlist})} where \var{hostname} is the primary host name
\var{ip_address}, \code{aliaslist} is a (possibly empty) list of responding to the given \var{ip_address}, \var{aliaslist} is a
alternative host names for the same address, and \code{ipaddrlist} is (possibly empty) list of alternative host names for the same address,
a list of IP addresses for the same interface on the same and \var{ipaddrlist} is a list of IP addresses for the same interface
host (most likely containing only a single address). on the same host (most likely containing only a single address).
To find the fully qualified domain name, check \var{hostname} and the To find the fully qualified domain name, check \var{hostname} and the
items of \var{aliaslist} for an entry containing at least one period. items of \var{aliaslist} for an entry containing at least one period.
\end{funcdesc} \end{funcdesc}
@ -122,29 +122,29 @@ items of \var{aliaslist} for an entry containing at least one period.
\begin{funcdesc}{getprotobyname}{protocolname} \begin{funcdesc}{getprotobyname}{protocolname}
Translate an Internet protocol name (e.g. \code{'icmp'}) to a constant Translate an Internet protocol name (e.g. \code{'icmp'}) to a constant
suitable for passing as the (optional) third argument to the suitable for passing as the (optional) third argument to the
\code{socket()} function. This is usually only needed for sockets \function{socket()} function. This is usually only needed for sockets
opened in ``raw'' mode (\code{SOCK_RAW}); for the normal socket modes, opened in ``raw'' mode (\constant{SOCK_RAW}); for the normal socket
the correct protocol is chosen automatically if the protocol is modes, the correct protocol is chosen automatically if the protocol is
omitted or zero. omitted or zero.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getservbyname}{servicename\, protocolname} \begin{funcdesc}{getservbyname}{servicename, protocolname}
Translate an Internet service name and protocol name to a port number Translate an Internet service name and protocol name to a port number
for that service. The protocol name should be \code{'tcp'} or for that service. The protocol name should be \code{'tcp'} or
\code{'udp'}. \code{'udp'}.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{socket}{family\, type\optional{\, proto}} \begin{funcdesc}{socket}{family, type\optional{, proto}}
Create a new socket using the given address family, socket type and Create a new socket using the given address family, socket type and
protocol number. The address family should be \code{AF_INET} or protocol number. The address family should be \constant{AF_INET} or
\code{AF_UNIX}. The socket type should be \code{SOCK_STREAM}, \constant{AF_UNIX}. The socket type should be \constant{SOCK_STREAM},
\code{SOCK_DGRAM} or perhaps one of the other \samp{SOCK_} constants. \constant{SOCK_DGRAM} or perhaps one of the other \samp{SOCK_} constants.
The protocol number is usually zero and may be omitted in that case. The protocol number is usually zero and may be omitted in that case.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{fromfd}{fd\, family\, type\optional{\, proto}} \begin{funcdesc}{fromfd}{fd, family, type\optional{, proto}}
Build a socket object from an existing file descriptor (an integer as Build a socket object from an existing file descriptor (an integer as
returned by a file object's \code{fileno} method). Address family, returned by a file object's \method{fileno()} method). Address family,
socket type and protocol number are as for the \code{socket} function socket type and protocol number are as for the \code{socket} function
above. The file descriptor should refer to a socket, but this is not above. The file descriptor should refer to a socket, but this is not
checked --- subsequent operations on the object may fail if the file checked --- subsequent operations on the object may fail if the file
@ -180,15 +180,14 @@ no-op; otherwise, it performs a 2-byte swap operation.
\begin{datadesc}{SocketType} \begin{datadesc}{SocketType}
This is a Python type object that represents the socket object type. This is a Python type object that represents the socket object type.
It is the same as \code{type(socket.socket(...))}. It is the same as \code{type(socket(...))}.
\end{datadesc} \end{datadesc}
\subsection{Socket Objects} \subsection{Socket Objects}
\noindent
Socket objects have the following methods. Except for Socket objects have the following methods. Except for
\code{makefile()} these correspond to \UNIX{} system calls applicable to \method{makefile()} these correspond to \UNIX{} system calls
sockets. applicable to sockets.
\setindexsubitem{(socket method)} \setindexsubitem{(socket method)}
\begin{funcdesc}{accept}{} \begin{funcdesc}{accept}{}
@ -213,19 +212,20 @@ Sockets are automatically closed when they are garbage-collected.
\begin{funcdesc}{connect}{address} \begin{funcdesc}{connect}{address}
Connect to a remote socket at \var{address}. Connect to a remote socket at \var{address}.
(The format of \var{address} depends on the address family --- see above.) (The format of \var{address} depends on the address family --- see
above.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{connect_ex}{address} \begin{funcdesc}{connect_ex}{address}
Like \code{connect(\var{address})}, but return an error indicator Like \code{connect(\var{address})}, but return an error indicator
instead of raising an exception. The error indicator is 0 if the instead of raising an exception. The error indicator is 0 if the
operation succeeded, otherwise the value of the \code{errno} operation succeeded, otherwise the value of the \cdata{errno}
variable. This is useful e.g. for asynchronous connects. variable. This is useful e.g. for asynchronous connects.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{fileno}{} \begin{funcdesc}{fileno}{}
Return the socket's file descriptor (a small integer). This is useful Return the socket's file descriptor (a small integer). This is useful
with \code{select}. with \function{select.select()}.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getpeername}{} \begin{funcdesc}{getpeername}{}
@ -242,16 +242,16 @@ number of an IP socket, for instance.
see above.) see above.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{getsockopt}{level\, optname\optional{\, buflen}} \begin{funcdesc}{getsockopt}{level, optname\optional{, buflen}}
Return the value of the given socket option (see the \UNIX{} man page Return the value of the given socket option (see the \UNIX{} man page
\emph{getsockopt}(2)). The needed symbolic constants (\code{SO_*} etc.) \manpage{getsockopt}{2}). The needed symbolic constants
are defined in this module. If \var{buflen} (\constant{SO_*} etc.) are defined in this module. If \var{buflen}
is absent, an integer option is assumed and its integer value is absent, an integer option is assumed and its integer value
is returned by the function. If \var{buflen} is present, it specifies is returned by the function. If \var{buflen} is present, it specifies
the maximum length of the buffer used to receive the option in, and the maximum length of the buffer used to receive the option in, and
this buffer is returned as a string. It is up to the caller to decode this buffer is returned as a string. It is up to the caller to decode
the contents of the buffer (see the optional built-in module the contents of the buffer (see the optional built-in module
\code{struct} for a way to decode C structures encoded as strings). \module{struct} for a way to decode C structures encoded as strings).
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{listen}{backlog} \begin{funcdesc}{listen}{backlog}
@ -262,42 +262,42 @@ least 1; the maximum value is system-dependent (usually 5).
\begin{funcdesc}{makefile}{\optional{mode\optional{\, bufsize}}} \begin{funcdesc}{makefile}{\optional{mode\optional{\, bufsize}}}
Return a \dfn{file object} associated with the socket. (File objects Return a \dfn{file object} associated with the socket. (File objects
were described earlier under Built-in Types.) The file object were described earlier in \ref{bltin-file-objects}, ``File Objects.'')
references a \code{dup()}ped version of the socket file descriptor, so The file object references a \cfunction{dup()}ped version of the
the file object and socket object may be closed or garbage-collected socket file descriptor, so the file object and socket object may be
independently. The optional \var{mode} and \var{bufsize} arguments closed or garbage-collected independently. The optional \var{mode}
are interpreted the same way as by the built-in and \var{bufsize} arguments are interpreted the same way as by the
\code{open()} function. built-in \function{open()} function.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{recv}{bufsize\optional{\, flags}} \begin{funcdesc}{recv}{bufsize\optional{, flags}}
Receive data from the socket. The return value is a string representing Receive data from the socket. The return value is a string representing
the data received. The maximum amount of data to be received the data received. The maximum amount of data to be received
at once is specified by \var{bufsize}. See the \UNIX{} manual page at once is specified by \var{bufsize}. See the \UNIX{} manual page
for the meaning of the optional argument \var{flags}; it defaults to \manpage{recv}{2} for the meaning of the optional argument
zero. \var{flags}; it defaults to zero.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{recvfrom}{bufsize\optional{\, flags}} \begin{funcdesc}{recvfrom}{bufsize\optional{, flags}}
Receive data from the socket. The return value is a pair Receive data from the socket. The return value is a pair
\code{(\var{string}, \var{address})} where \var{string} is a string \code{(\var{string}, \var{address})} where \var{string} is a string
representing the data received and \var{address} is the address of the representing the data received and \var{address} is the address of the
socket sending the data. The optional \var{flags} argument has the socket sending the data. The optional \var{flags} argument has the
same meaning as for \code{recv()} above. same meaning as for \method{recv()} above.
(The format of \var{address} depends on the address family --- see above.) (The format of \var{address} depends on the address family --- see above.)
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{send}{string\optional{\, flags}} \begin{funcdesc}{send}{string\optional{, flags}}
Send data to the socket. The socket must be connected to a remote Send data to the socket. The socket must be connected to a remote
socket. The optional \var{flags} argument has the same meaning as for socket. The optional \var{flags} argument has the same meaning as for
\code{recv()} above. Return the number of bytes sent. \method{recv()} above. Returns the number of bytes sent.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{sendto}{string\optional{\, flags}\, address} \begin{funcdesc}{sendto}{string\optional{\, flags}\, address}
Send data to the socket. The socket should not be connected to a Send data to the socket. The socket should not be connected to a
remote socket, since the destination socket is specified by remote socket, since the destination socket is specified by
\code{address}. The optional \var{flags} argument has the same \var{address}. The optional \var{flags} argument has the same
meaning as for \code{recv()} above. Return the number of bytes sent. meaning as for \method{recv()} above. Return the number of bytes sent.
(The format of \var{address} depends on the address family --- see above.) (The format of \var{address} depends on the address family --- see above.)
\end{funcdesc} \end{funcdesc}
@ -305,30 +305,32 @@ meaning as for \code{recv()} above. Return the number of bytes sent.
Set blocking or non-blocking mode of the socket: if \var{flag} is 0, Set blocking or non-blocking mode of the socket: if \var{flag} is 0,
the socket is set to non-blocking, else to blocking mode. Initially the socket is set to non-blocking, else to blocking mode. Initially
all sockets are in blocking mode. In non-blocking mode, if a all sockets are in blocking mode. In non-blocking mode, if a
\code{recv} call doesn't find any data, or if a \code{send} call can't \method{recv()} call doesn't find any data, or if a \code{send} call can't
immediately dispose of the data, a \code{socket.error} exception is immediately dispose of the data, a \exception{error} exception is
raised; in blocking mode, the calls block until they can proceed. raised; in blocking mode, the calls block until they can proceed.
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{setsockopt}{level\, optname\, value} \begin{funcdesc}{setsockopt}{level\, optname\, value}
Set the value of the given socket option (see the \UNIX{} man page Set the value of the given socket option (see the \UNIX{} man page
\emph{setsockopt}(2)). The needed symbolic constants are defined in \manpage{setsockopt}{2}). The needed symbolic constants are defined in
the \code{socket} module (\code{SO_*} etc.). The value can be an the \module{socket} module (\code{SO_*} etc.). The value can be an
integer or a string representing a buffer. In the latter case it is integer or a string representing a buffer. In the latter case it is
up to the caller to ensure that the string contains the proper bits up to the caller to ensure that the string contains the proper bits
(see the optional built-in module (see the optional built-in module
\code{struct} for a way to encode C structures as strings). \module{struct}\refbimodindex{struct} for a way to encode C structures
as strings).
\end{funcdesc} \end{funcdesc}
\begin{funcdesc}{shutdown}{how} \begin{funcdesc}{shutdown}{how}
Shut down one or both halves of the connection. If \var{how} is \code{0}, Shut down one or both halves of the connection. If \var{how} is
further receives are disallowed. If \var{how} is \code{1}, further sends are \code{0}, further receives are disallowed. If \var{how} is \code{1},
disallowed. If \var{how} is \code{2}, further sends and receives are further sends are disallowed. If \var{how} is \code{2}, further sends
disallowed. and receives are disallowed.
\end{funcdesc} \end{funcdesc}
Note that there are no methods \code{read()} or \code{write()}; use Note that there are no methods \method{read()} or \method{write()};
\code{recv()} and \code{send()} without \var{flags} argument instead. use \method{recv()} and \method{send()} without \var{flags} argument
instead.
\subsection{Example} \subsection{Example}
\nodename{Socket Example} \nodename{Socket Example}
@ -336,12 +338,13 @@ Note that there are no methods \code{read()} or \code{write()}; use
Here are two minimal example programs using the TCP/IP protocol:\ a Here are two minimal example programs using the TCP/IP protocol:\ a
server that echoes all data that it receives back (servicing only one server that echoes all data that it receives back (servicing only one
client), and a client using it. Note that a server must perform the client), and a client using it. Note that a server must perform the
sequence \code{socket}, \code{bind}, \code{listen}, \code{accept} sequence \function{socket()}, \method{bind()}, \method{listen()},
(possibly repeating the \code{accept} to service more than one client), \method{accept()} (possibly repeating the \method{accept()} to service
while a client only needs the sequence \code{socket}, \code{connect}. more than one client), while a client only needs the sequence
Also note that the server does not \code{send}/\code{receive} on the \function{socket()}, \method{connect()}. Also note that the server
does not \method{send()}/\method{recv()} on the
socket it is listening on but on the new socket returned by socket it is listening on but on the new socket returned by
\code{accept}. \method{accept()}.
\begin{verbatim} \begin{verbatim}
# Echo server program # Echo server program
@ -359,7 +362,7 @@ while 1:
conn.send(data) conn.send(data)
conn.close() conn.close()
\end{verbatim} \end{verbatim}
%
\begin{verbatim} \begin{verbatim}
# Echo client program # Echo client program
from socket import * from socket import *
@ -372,7 +375,7 @@ data = s.recv(1024)
s.close() s.close()
print 'Received', `data` print 'Received', `data`
\end{verbatim} \end{verbatim}
%
\begin{seealso} \begin{seealso}
\seemodule{SocketServer}{classes that simplify writing network servers} \seemodule{SocketServer}{classes that simplify writing network servers}
\end{seealso} \end{seealso}