support tcp pub/sub.

lichao

2021-06-30 ae17d1439b35b55212c3a30712e0a60b1d6a99c0

 box/center.cpp

@@ -146,7 +146,7 @@
            replyer(reply);
            auto hosts = center->FindRemoteSubClients(pub.topic());
            for (auto &host : hosts) {
               tcp_proxy.Publish(host, kBHCenterPort, pub.SerializeAsString());
               tcp_proxy.Publish(host, kBHCenterPort, msg.content());
            }
         }
      };