import asynchatimport socketimport errnoclass vischat (asynchat.async_chat):    def __init__ (self, host, port):        self.host = host        self.port = port        self.outstanding = []        self.lines = []        self.buffer = ""        asynchat.async_chat.__init__ (self)    def handle_connect (self):        err = self.getsockopt (socket.SOL_SOCKET, socket.SO_ERROR)        if err == errno.ECONNREFUSED:            self.connect_cb (None)        else:            self.connect_cb (self)    def start_connect (self, cb):        self.create_socket (socket.AF_INET, socket.SOCK_STREAM)        self.connect ((self.host, self.port))        self.set_terminator ("\n")        self.connect_cb = cb    def collect_incoming_data (self, data):        self.buffer += data            def found_terminator (self):        # Assumes that vis handles all request in order.        # print "### %s" % self.buffer        if self.buffer[0] == '.':            z = self.outstanding.pop (0)            if z:                z (self.lines)            self.lines = []        else:            self.lines.append (self.buffer)        self.buffer = ""    # Each command here is a front-end to a real message that could get    # sent to vis, and a callback that should notify     def list (self, cb):        self.push ("list\n")        self.outstanding.append (cb)    def arc (self, a, b):        self.push ("arc %s %s\n" % (a, b))        self.outstanding.append (None)    def arrow (self, a, b):        self.push ("arrow %s %s\n" % (a, b))        self.outstanding.append (None)    def reset (self):        self.push ("reset\n")        self.outstanding.append (None)    def highlight (self, a):        self.push ("highlight %s\n" % a)        self.outstanding.append (None)    def select (self, a):        self.push ("select %s\n" % a)        self.outstanding.append (None)