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POhow do I avoid the infinite loop when using the paramiko port forward demo?
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copied!<p>I need use port forwarding in Python to communicate with a remote MySQL DB through an SSH tunnel. I downloaded the paramiko package and tried out the port forwarding demo (forward.py). It works very nicely, but I am having trouble integrating it into my own scripts (similar to the one below). When the main forwarding function is called it enters an infinite loop and the rest of my code does not execute. How can I use the forward.py demo and get past the infinite loop?</p> <p>My script:</p> <pre><code>import paramiko import forward import MySQLdb import cfg import sys client = paramiko.SSHClient() client.load_system_host_keys() client.set_missing_host_key_policy(paramiko.WarningPolicy()) try: client.connect(cfg.remhost, cfg.remport, username=cfg.user, password=cfg.password) except Exception, e: print '*** Failed to connect to %s:%d: %r' % (cfg.remhost, cfg.remport, e) sys.exit(1) try: forward.forward_tunnel(3306, cfg.remhost, 3306, client.get_transport()) except KeyboardInterrupt: print 'C-c: Port forwarding stopped.' sys.exit(0) try: db = MySQLdb.connect('127.0.0.1', cfg.dbuser, cfg.dbpass, cfg.dbname) except Exception, e: print 'Failed to connect to database' sys.exit(1) try: cursor = self.db.cursor(MySQLdb.cursors.DictCursor) sql = 'SELECT * FROM ' + cfg.dbtable cursor.execute(sql) results = cursor.fetchall() print str(len(results)) except Exception, e: print 'Failed to query database' sys.exit(1) </code></pre> <p>Here is the main chunk of the forward.py demo code:</p> <pre><code>class ForwardServer (SocketServer.ThreadingTCPServer): daemon_threads = True allow_reuse_address = True class Handler (SocketServer.BaseRequestHandler): def handle(self): try: chan = self.ssh_transport.open_channel('direct-tcpip', (self.chain_host, self.chain_port), self.request.getpeername()) except Exception, e: verbose('Incoming request to %s:%d failed: %s' % (self.chain_host, self.chain_port, repr(e))) return if chan is None: verbose('Incoming request to %s:%d was rejected by the SSH server.' % (self.chain_host, self.chain_port)) return verbose('Connected! Tunnel open %r -> %r -> %r' % (self.request.getpeername(), chan.getpeername(), (self.chain_host, self.chain_port))) while True: r, w, x = select.select([self.request, chan], [], []) if self.request in r: data = self.request.recv(1024) if len(data) == 0: break chan.send(data) if chan in r: data = chan.recv(1024) if len(data) == 0: break self.request.send(data) chan.close() self.request.close() verbose('Tunnel closed from %r' % (self.request.getpeername(),)) def forward_tunnel(local_port, remote_host, remote_port, transport): # this is a little convoluted, but lets me configure things for the Handler # object. (SocketServer doesn't give Handlers any way to access the outer # server normally.) class SubHander (Handler): chain_host = remote_host chain_port = remote_port ssh_transport = transport ForwardServer(('', local_port), SubHander).serve_forever() def verbose(s): if g_verbose: print s </code></pre>

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