add examples/portforwarder.py

examples/portforwarder.py

+import sys
+import gevent
+from gevent.server import StreamServer
+from gevent.socket import create_connection, gethostbyname
+
+
+class PortForwarder(StreamServer):
+
+    def __init__(self, listener, dest, **kwargs):
+        StreamServer.__init__(self, listener, **kwargs)
+        self.dest = dest
+
+    def handle(self, source, address):
+        log('%s:%s accepted', *address[:2])
+        dest = create_connection(self.dest)
+        forwarder1 = gevent.spawn(forward, source, dest)
+        forwarder2 = gevent.spawn(forward, dest, source)
+        gevent.joinall([forwarder1, forwarder2], count=1)
+
+
+def forward(source, dest):
+    source_address = '%s:%s' % source.getpeername()[:2]
+    dest_address = '%s:%s' % dest.getpeername()[:2]
+    try:
+        while True:
+            data = source.recv(1024)
+            log('%s->%s: %r', source_address, dest_address, data)
+            if not data:
+                break
+            dest.sendall(data)
+    finally:
+        source.close()
+        dest.close()
+
+
+def parse_address(address):
+    try:
+        hostname, port = address.rsplit(':', 1)
+        port = int(port)
+    except ValueError:
+        sys.exit('Expected HOST:PORT: %r' % address)
+    return gethostbyname(hostname), port
+
+
+def main():
+    args = sys.argv[1:]
+    if len(args) != 2:
+        sys.exit('Usage: %s source-address destination-address' % __file__)
+    source = args[0]
+    dest = parse_address(args[1])
+    server = PortForwarder(source, dest)
+    log('Starting port forwarder %s:%s -> %s:%s', *(server.address[:2] + dest))
+    server.serve_forever()
+
+
+def log(message, *args):
+    message = message % args
+    sys.stderr.write(message + '\n')
+
+
+if __name__ == '__main__':
+    main()