Decided to add the telnet library that I wrote long ago (it's still in
the Demos/cwilib directory). Converted comments to doc strings and
used default arguments instead of *args. Updated the example.
diff --git a/Lib/telnetlib.py b/Lib/telnetlib.py
new file mode 100644
index 0000000..4595426
--- /dev/null
+++ b/Lib/telnetlib.py
@@ -0,0 +1,424 @@
+"""TELNET client class.
+
+Based on RFC 854: TELNET Protocol Specification, by J. Postel and
+J. Reynolds
+
+Example:
+
+>>> from telnetlib import Telnet
+>>> tn = Telnet('www.python.org', 79) # connect to finger port
+>>> tn.write('guido\r\n')
+>>> print tn.read_all()
+Login Name TTY Idle When Where
+guido Guido van Rossum pts/2 <Dec 2 11:10> snag.cnri.reston..
+
+>>>
+
+Note that read_all() won't read until eof -- it just reads some data
+-- but it guarantees to read at least one byte unless EOF is hit.
+
+It is possible to pass a Telnet object to select.select() in order to
+wait until more data is available. Note that in this case,
+read_eager() may return '' even if there was data on the socket,
+because the protocol negotiation may have eaten the data. This is why
+EOFError is needed in some cases to distinguish between "no data" and
+"connection closed" (since the socket also appears ready for reading
+when it is closed).
+
+Bugs:
+- may hang when connection is slow in the middle of an IAC sequence
+
+To do:
+- option negotiation
+
+"""
+
+
+# Imported modules
+import socket
+import select
+import string
+import regsub
+
+# Tunable parameters
+DEBUGLEVEL = 0
+
+# Telnet protocol defaults
+TELNET_PORT = 23
+
+# Telnet protocol characters (don't change)
+IAC = chr(255) # "Interpret As Command"
+DONT = chr(254)
+DO = chr(253)
+WONT = chr(252)
+WILL = chr(251)
+theNULL = chr(0)
+
+
+class Telnet:
+
+ """Telnet interface class.
+
+ An instance of this class represents a connection to a telnet
+ server. The instance is initially not connected; the open()
+ method must be used to establish a connection. Alternatively, the
+ host name and optional port number can be passed to the
+ constructor, too.
+
+ Don't try to reopen an already connected instance.
+
+ This class has many read_*() methods. Note that some of them
+ raise EOFError when the end of the connection is read, because
+ they can return an empty string for other reasons. See the
+ individual doc strings.
+
+ read_until(expected, [timeout])
+ Read until the expected string has been seen, or a timeout is
+ hit (default is no timeout); may block.
+
+ read_all()
+ Read all data until EOF; may block.
+
+ read_some()
+ Read at least one byte or EOF; may block.
+
+ read_very_eager()
+ Read all data available already queued or on the socket,
+ without blocking.
+
+ read_eager()
+ Read either data already queued or some data available on the
+ socket, without blocking.
+
+ read_lazy()
+ Read all data in the raw queue (processing it first), without
+ doing any socket I/O.
+
+ read_very_lazy()
+ Reads all data in the cooked queue, without doing any socket
+ I/O.
+
+ """
+
+ def __init__(self, host=None, port=0):
+ """Constructor.
+
+ When called without arguments, create an unconnected instance.
+ With a hostname argument, it connects the instance; a port
+ number is optional.
+
+ """
+ self.debuglevel = DEBUGLEVEL
+ self.host = host
+ self.port = port
+ self.sock = None
+ self.rawq = ''
+ self.irawq = 0
+ self.cookedq = ''
+ self.eof = 0
+ if host:
+ self.open(host, port)
+
+ def open(self, host, port=0):
+ """Connect to a host.
+
+ The optional second argument is the port number, which
+ defaults to the standard telnet port (23).
+
+ Don't try to reopen an already connected instance.
+
+ """
+ self.eof = 0
+ if not port:
+ port = TELNET_PORT
+ self.host = host
+ self.port = port
+ self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+ self.sock.connect((self.host, self.port))
+
+ def __del__(self):
+ """Destructor -- close the connection."""
+ self.close()
+
+ def msg(self, msg, *args):
+ """Print a debug message, when the debug level is > 0.
+
+ If extra arguments are present, they are substituted in the
+ message using the standard string formatting operator.
+
+ """
+ if self.debuglevel > 0:
+ print 'Telnet(%s,%d):' % (self.host, self.port),
+ if args:
+ print msg % args
+ else:
+ print msg
+
+ def set_debuglevel(self, debuglevel):
+ """Set the debug level.
+
+ The higher it is, the more debug output you get (on sys.stdout).
+
+ """
+ self.debuglevel = debuglevel
+
+ def close(self):
+ """Close the connection."""
+ if self.sock:
+ self.sock.close()
+ self.sock = 0
+ self.eof = 1
+
+ def get_socket(self):
+ """Return the socket object used internally."""
+ return self.sock
+
+ def fileno(self):
+ """Return the fileno() of the socket object used internally."""
+ return self.sock.fileno()
+
+ def write(self, buffer):
+ """Write a string to the socket, doubling any IAC characters.
+
+ Can block if the connection is blocked. May raise
+ socket.error if the connection is closed.
+
+ """
+ if IAC in buffer:
+ buffer = regsub.gsub(IAC, IAC+IAC, buffer)
+ self.sock.send(buffer)
+
+ def read_until(self, match, timeout=None):
+ """Read until a given string is encountered or until timeout.
+
+ When no match is found, return whatever is available instead,
+ possibly the empty string. Raise EOFError if the connection
+ is closed and no cooked data is available.
+
+ """
+ n = len(match)
+ self.process_rawq()
+ i = string.find(self.cookedq, match)
+ if i >= 0:
+ i = i+n
+ buf = self.cookedq[:i]
+ self.cookedq = self.cookedq[i:]
+ return buf
+ s_reply = ([self], [], [])
+ s_args = s_reply
+ if timeout is not None:
+ s_args = s_args + (timeout,)
+ while not self.eof and apply(select.select, s_args) == s_reply:
+ i = max(0, len(self.cookedq)-n)
+ self.fill_rawq()
+ self.process_rawq()
+ i = string.find(self.cookedq, match, i)
+ if i >= 0:
+ i = i+n
+ buf = self.cookedq[:i]
+ self.cookedq = self.cookedq[i:]
+ return buf
+ return self.read_very_lazy()
+
+ def read_all(self):
+ """Read all data until EOF; block until connection closed."""
+ self.process_rawq()
+ while not self.eof:
+ self.fill_rawq()
+ self.process_rawq()
+ buf = self.cookedq
+ self.cookedq = ''
+ return buf
+
+ def read_some(self):
+ """Read at least one byte of cooked data unless EOF is hit.
+
+ Return '' if EOF is hit. Block if no data is immediately
+ available.
+
+ """
+ self.process_rawq()
+ while not self.cookedq and not self.eof:
+ self.fill_rawq()
+ self.process_rawq()
+ buf = self.cookedq
+ self.cookedq = ''
+ return buf
+
+ def read_very_eager(self):
+ """Read everything that's possible without blocking in I/O (eager).
+
+ Raise EOFError if connection closed and no cooked data
+ available. Return '' if no cooked data available otherwise.
+ Don't block unless in the midst of an IAC sequence.
+
+ """
+ self.process_rawq()
+ while not self.eof and self.sock_avail():
+ self.fill_rawq()
+ self.process_rawq()
+ return self.read_very_lazy()
+
+ def read_eager(self):
+ """Read readily available data.
+
+ Raise EOFError if connection closed and no cooked data
+ available. Return '' if no cooked data available otherwise.
+ Don't block unless in the midst of an IAC sequence.
+
+ """
+ self.process_rawq()
+ while not self.cookedq and not self.eof and self.sock_avail():
+ self.fill_rawq()
+ self.process_rawq()
+ return self.read_very_lazy()
+
+ def read_lazy(self):
+ """Process and return data that's already in the queues (lazy).
+
+ Raise EOFError if connection closed and no data available.
+ Return '' if no cooked data available otherwise. Don't block
+ unless in the midst of an IAC sequence.
+
+ """
+ self.process_rawq()
+ return self.read_very_lazy()
+
+ def read_very_lazy(self):
+ """Return any data available in the cooked queue (very lazy).
+
+ Raise EOFError if connection closed and no data available.
+ Return '' if no cooked data available otherwise. Don't block.
+
+ """
+ buf = self.cookedq
+ self.cookedq = ''
+ if not buf and self.eof and not self.rawq:
+ raise EOFError, 'telnet connection closed'
+ return buf
+
+ def process_rawq(self):
+ """Transfer from raw queue to cooked queue.
+
+ Set self.eof when connection is closed. Don't block unless in
+ the midst of an IAC sequence.
+
+ """
+ buf = ''
+ try:
+ while self.rawq:
+ c = self.rawq_getchar()
+ if c == theNULL:
+ continue
+ if c == "\021":
+ continue
+ if c != IAC:
+ buf = buf + c
+ continue
+ c = self.rawq_getchar()
+ if c == IAC:
+ buf = buf + c
+ elif c in (DO, DONT):
+ opt = self.rawq_getchar()
+ self.msg('IAC %s %d', c == DO and 'DO' or 'DONT', ord(c))
+ self.sock.send(IAC + WONT + opt)
+ elif c in (WILL, WONT):
+ opt = self.rawq_getchar()
+ self.msg('IAC %s %d',
+ c == WILL and 'WILL' or 'WONT', ord(c))
+ else:
+ self.msg('IAC %s not recognized' % `c`)
+ except EOFError: # raised by self.rawq_getchar()
+ pass
+ self.cookedq = self.cookedq + buf
+
+ def rawq_getchar(self):
+ """Get next char from raw queue.
+
+ Block if no data is immediately available. Raise EOFError
+ when connection is closed.
+
+ """
+ if not self.rawq:
+ self.fill_rawq()
+ if self.eof:
+ raise EOFError
+ c = self.rawq[self.irawq]
+ self.irawq = self.irawq + 1
+ if self.irawq >= len(self.rawq):
+ self.rawq = ''
+ self.irawq = 0
+ return c
+
+ def fill_rawq(self):
+ """Fill raw queue from exactly one recv() system call.
+
+ Block if no data is immediately available. Set self.eof when
+ connection is closed.
+
+ """
+ if self.irawq >= len(self.rawq):
+ self.rawq = ''
+ self.irawq = 0
+ # The buffer size should be fairly small so as to avoid quadratic
+ # behavior in process_rawq() above
+ buf = self.sock.recv(50)
+ self.eof = (not buf)
+ self.rawq = self.rawq + buf
+
+ def sock_avail(self):
+ """Test whether data is available on the socket."""
+ return select.select([self], [], [], 0) == ([self], [], [])
+
+ def interact(self):
+ """Interaction function, emulates a very dumb telnet client."""
+ import sys, select
+ while 1:
+ rfd, wfd, xfd = select.select([self, sys.stdin], [], [])
+ if sys.stdin in rfd:
+ line = sys.stdin.readline()
+ self.write(line)
+ if self in rfd:
+ try:
+ text = self.read_eager()
+ except EOFError:
+ print '*** Connection closed by remote host ***'
+ break
+ if text:
+ sys.stdout.write(text)
+ sys.stdout.flush()
+ self.close()
+
+
+
+def test():
+ """Test program for telnetlib.
+
+ Usage: python telnetlib.py [-d] ... [host [port]]
+
+ Default host is localhost; default port is 23.
+
+ """
+ import sys
+ debuglevel = 0
+ while sys.argv[1:] and sys.argv[1] == '-d':
+ debuglevel = debuglevel+1
+ del sys.argv[1]
+ host = 'localhost'
+ if sys.argv[1:]:
+ host = sys.argv[1]
+ port = 0
+ if sys.argv[2:]:
+ portstr = sys.argv[2]
+ try:
+ port = int(portstr)
+ except ValueError:
+ port = socket.getservbyname(portstr, 'tcp')
+ tn = Telnet()
+ tn.set_debuglevel(debuglevel)
+ tn.open(host, port)
+ tn.interact()
+ tn.close()
+
+if __name__ == '__main__':
+ test()