Initial revision

Demo/sockets/telnet.py

@@ -0,0 +1,109 @@
+#! /usr/local/python
+
+# Minimal interface to the Internet telnet protocol.
+#
+# It refuses all telnet options and does not recognize any of the other
+# telnet commands, but can still be used to connect in line-by-line mode.
+# It's also useful to play with a number of other services,
+# like time, finger, smtp and even ftp.
+#
+# Usage: telnet host [port]
+#
+# The port may be a service name or a decimal port number;
+# it defaults to 'telnet'.
+
+
+import sys, posix, time
+from socket import *
+
+BUFSIZE = 1024
+
+# Telnet protocol characters
+
+IAC  = chr(255)	# Interpret as command
+DONT = chr(254)
+DO   = chr(253)
+WONT = chr(252)
+WILL = chr(251)
+
+def main():
+	host = sys.argv[1]
+	try:
+		hostaddr = gethostbyname(host)
+	except error:
+		sys.stderr.write(sys.argv[1] + ': bad host name\n')
+		sys.exit(2)
+	#
+	if len(sys.argv) > 2:
+		servname = sys.argv[2]
+	else:
+		servname = 'telnet'
+	#
+	if '0' <= servname[:1] <= '9':
+		port = eval(servname)
+	else:
+		try:
+			port = getservbyname(servname, 'tcp')
+		except error:
+			sys.stderr.write(servname + ': bad tcp service name\n')
+			sys.exit(2)
+	#
+	s = socket(AF_INET, SOCK_STREAM)
+	#
+	try:
+		s.connect(host, port)
+	except error, msg:
+		sys.stderr.write('connect failed: ' + `msg` + '\n')
+		sys.exit(1)
+	#
+	pid = posix.fork()
+	#
+	if pid = 0:
+		# child -- read stdin, write socket
+		while 1:
+			line = sys.stdin.readline()
+			s.send(line)
+	else:
+		# parent -- read socket, write stdout
+		iac = 0		# Interpret next char as command
+		opt = ''	# Interpret next char as option
+		while 1:
+			data = s.recv(BUFSIZE)
+			if not data:
+				# EOF; kill child and exit
+				sys.stderr.write( '(Closed by remote host)\n')
+				posix.kill(pid, 9)
+				sys.exit(1)
+			cleandata = ''
+			for c in data:
+				if opt:
+					print ord(c)
+					s.send(opt + c)
+					opt = ''
+				elif iac:
+					iac = 0
+					if c = IAC:
+						cleandata = cleandata + c
+					elif c in (DO, DONT):
+						if c = DO: print '(DO)',
+						else: print '(DONT)',
+						opt = IAC + WONT
+					elif c in (WILL, WONT):
+						if c = WILL: print '(WILL)',
+						else: print '(WONT)',
+						opt = IAC + DONT
+					else:
+						print '(command)', ord(c)
+				elif c = IAC:
+					iac = 1
+					print '(IAC)',
+				else:
+					cleandata = cleandata + c
+			sys.stdout.write(cleandata)
+			sys.stdout.flush()
+
+
+try:
+	main()
+except KeyboardInterrupt:
+	pass