use default if request port is 0.

lichao

2021-06-01 7c8e2433992aac41bdeb0d7d0861b738d9866628

 box/center.cpp

@@ -104,7 +104,11 @@
                     center->PassRemoteReplyToLocal(dest, head, std::move(body_content));
                  }
               };
               if (!tcp_proxy.Request(head.dest().ip(), head.dest().port(), msg.content(), onResult)) {
               uint16_t port = head.dest().port();
               if (port == 0) {
                  port = kBHCenterPort;
               }
               if (!tcp_proxy.Request(head.dest().ip(), port, msg.content(), onResult)) {
                  replyer(MakeReply<Reply>(eError, "send request failed."));
               } else {
                  // success