Per @tilgovi in issue gevent/gevent#248, try the path of adapting the example...

Per @tilgovi in issue gevent/gevent#248, try the path of adapting the example portforwarder to work like gunicorn and don't expect the lifetime of the socket to outlast the invocation of the spawned handle method. Down to 10 total failures, only one unexpected.

examples/portforwarder.py

@@ -31,9 +31,11 @@ class PortForwarder(StreamServer):
         except IOError as ex:
             log('%s:%s failed to connect to %s:%s: %s', address[0], address[1], self.dest[0], self.dest[1], ex)
             return
-        gevent.spawn(forward, source, dest)
-        gevent.spawn(forward, dest, source)
-        # XXX only one spawn() is needed
+        forwarders = (gevent.spawn(forward, source, dest),
+                      gevent.spawn(forward, dest, source))
+        # if we return from this method, the stream will be closed out
+        # from under us, so wait for our children
+        gevent.joinall(forwarders)
 
     def close(self):
         if self.closed: