How do server create stream, and write message to client using stream

[FredyVia]

modified from streaming_echo_c++ example
here is my client.cpp

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

// A client sending requests to server in batch every 1 second.

#include "echo.pb.h"
#include <brpc/channel.h>
#include <brpc/stream.h>
#include <butil/logging.h>
#include <gflags/gflags.h>
#include <glog/logging.h>

DEFINE_bool(send_attachment, true, "Carry attachment along with requests");
DEFINE_string(connection_type, "",
              "Connection type. Available values: single, pooled, short");
DEFINE_string(server, "0.0.0.0:8001", "IP Address of server");
DEFINE_int32(timeout_ms, 100, "RPC timeout in milliseconds");
DEFINE_int32(max_retry, 3, "Max retries(not including the first RPC)");

class StreamReceiver : public brpc::StreamInputHandler {
public:
  virtual int on_received_messages(brpc::StreamId id,
                                   butil::IOBuf *const messages[],
                                   size_t size) {
    for (size_t i = 0; i < size; ++i) {
      LOG(INFO) << "msg[" << i << "]=" << *messages[i];
    }
    return 0;
  }
  virtual void on_idle_timeout(brpc::StreamId id) {
    LOG(INFO) << "Stream=" << id << " has no data transmission for a while";
  }
  virtual void on_closed(brpc::StreamId id) {
    LOG(INFO) << "Stream=" << id << " is closed";
  }
};

int main(int argc, char *argv[]) {
  // Parse gflags. We recommend you to use gflags as well.
  google::ParseCommandLineFlags(&argc, &argv, true);

  // A Channel represents a communication line to a Server. Notice that
  // Channel is thread-safe and can be shared by all threads in your program.
  brpc::Channel channel;

  // Initialize the channel, NULL means using default options.
  brpc::ChannelOptions options;
  options.protocol = brpc::PROTOCOL_BAIDU_STD;
  options.connection_type = FLAGS_connection_type;
  options.timeout_ms = FLAGS_timeout_ms /*milliseconds*/;
  options.max_retry = FLAGS_max_retry;
  if (channel.Init(FLAGS_server.c_str(), &options) != 0) {
    LOG(ERROR) << "Fail to initialize channel";
    return -1;
  }

  // Normally, you should not call a Channel directly, but instead construct
  // a stub Service wrapping it. stub can be shared by all threads as well.
  example::FileService_Stub stub(&channel);
  brpc::Controller cntl;
  brpc::StreamId stream1, stream2;
  if (brpc::StreamCreate(&stream1, cntl, nullptr) != 0) {
    LOG(ERROR) << "Fail to create stream1";
    return -1;
  }
  LOG(INFO) << "Created Stream=" << stream1;
  example::PutRequest put_request;
  example::PutResponse put_response;
  put_request.set_message("I'm a RPC to connect stream1");
  stub.put(&cntl, &put_request, &put_response, NULL);
  if (cntl.Failed()) {
    LOG(ERROR) << "Fail to connect stream1, " << cntl.ErrorText();
    return -1;
  }

  for (int i = 0; i < 3; i++) {
    butil::IOBuf msg;
    msg.append("put: abcdefghijklmnopqrstuvwxyz");
    CHECK_EQ(0, brpc::StreamWrite(stream1, msg));
    sleep(1);
  }

  brpc::StreamClose(stream1);

  cntl.Reset();
  StreamReceiver *receiver = new StreamReceiver();
  brpc::StreamOptions stream_options;
  stream_options.handler = receiver;
  example::GetRequest get_request;
  example::GetResponse get_response;
  get_request.set_message("I'm a RPC to connect stream2");
  if (brpc::StreamCreate(&stream2, cntl, &stream_options) != 0) {
    LOG(ERROR) << "Fail to create stream";
  }

  stub.get(&cntl, &get_request, &get_response, NULL);
  LOG(INFO) << get_response.message();
  while (!brpc::IsAskedToQuit()) {
    LOG(INFO) << "waiting";
    sleep(1);
  }

  brpc::StreamClose(stream2);
  LOG(INFO) << "EchoClient is going to quit";
  return 0;
}

here is my server.cpp

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

// A server to receive EchoRequest and send back EchoResponse.

#include "echo.pb.h"
#include <brpc/server.h>
#include <brpc/stream.h>
#include <butil/logging.h>
#include <gflags/gflags.h>

DEFINE_bool(send_attachment, true, "Carry attachment along with response");
DEFINE_int32(port, 8001, "TCP Port of this server");
DEFINE_int32(idle_timeout_s, -1,
             "Connection will be closed if there is no "
             "read/write operations during the last `idle_timeout_s'");

class StreamReceiver : public brpc::StreamInputHandler {
public:
  virtual int on_received_messages(brpc::StreamId id,
                                   butil::IOBuf *const messages[],
                                   size_t size) {
    std::ostringstream os;
    for (size_t i = 0; i < size; ++i) {
      os << "msg[" << i << "]=" << *messages[i];
    }
    LOG(INFO) << "Received from Stream=" << id << ": " << os.str();
    return 0;
  }
  virtual void on_idle_timeout(brpc::StreamId id) {
    LOG(INFO) << "Stream=" << id << " has no data transmission for a while";
  }
  virtual void on_closed(brpc::StreamId id) {
    LOG(INFO) << "Stream=" << id << " is closed";
    brpc::StreamClose(id);
  }
};

// Your implementation of example::EchoService
class StreamingFileService : public example::FileService {
public:
  StreamingFileService() : stream_id(brpc::INVALID_STREAM_ID) {}
  virtual ~StreamingFileService() { brpc::StreamClose(stream_id); };
  virtual void get(google::protobuf::RpcController *controller,
                   const example::GetRequest *request,
                   example::GetResponse *response,
                   google::protobuf::Closure *done) {
    // This object helps you to call done->Run() in RAII style. If you need
    // to process the request asynchronously, pass done_guard.release().
    brpc::ClosureGuard done_guard(done);
    brpc::Controller *cntl = static_cast<brpc::Controller *>(controller);
    LOG(INFO) << request->message();

    if (brpc::StreamAccept(&stream_id, *cntl, nullptr) != 0) {
      cntl->SetFailed("Fail to accept stream");
      return;
    }
    LOG(INFO) << "accept stream success";
    for (int i = 0; i < 3; i++) {
      butil::IOBuf msg;
      msg.append("GET: ABCDEFGHIJKLMNOPQRSTUVWXYZ");
      LOG(INFO) << "writing";
      CHECK_EQ(0, brpc::StreamWrite(stream_id, msg));
      sleep(1);
    }
    response->set_message("Accepted stream");
  }

  virtual void put(google::protobuf::RpcController *controller,
                   const example::PutRequest *request,
                   example::PutResponse *response,
                   google::protobuf::Closure *done) {
    // This object helps you to call done->Run() in RAII style. If you need
    // to process the request asynchronously, pass done_guard.release().
    brpc::ClosureGuard done_guard(done);
    LOG(INFO) << request->message();

    brpc::Controller *cntl = static_cast<brpc::Controller *>(controller);
    brpc::StreamOptions stream_options;
    stream_options.handler = &_receiver;

    if (brpc::StreamAccept(&stream_id, *cntl, &stream_options) != 0) {
      cntl->SetFailed("Fail to accept stream");
      return;
    }
    response->set_message("Accepted stream");
  }

private:
  StreamReceiver _receiver;
  brpc::StreamId stream_id;
};

int main(int argc, char *argv[]) {
  // Parse gflags. We recommend you to use gflags as well.
  google::ParseCommandLineFlags(&argc, &argv, true);

  // Generally you only need one Server.
  brpc::Server server;

  // Instance of your service.
  StreamingFileService echo_service_impl;

  // Add the service into server. Notice the second parameter, because the
  // service is put on stack, we don't want server to delete it, otherwise
  // use brpc::SERVER_OWNS_SERVICE.
  if (server.AddService(&echo_service_impl, brpc::SERVER_DOESNT_OWN_SERVICE) !=
      0) {
    LOG(ERROR) << "Fail to add service";
    return -1;
  }

  // Start the server.
  brpc::ServerOptions options;
  options.idle_timeout_sec = FLAGS_idle_timeout_s;
  if (server.Start(FLAGS_port, &options) != 0) {
    LOG(ERROR) << "Fail to start EchoServer";
    return -1;
  }

  // Wait until Ctrl-C is pressed, then Stop() and Join() the server.
  server.RunUntilAskedToQuit();
  return 0;
}

here is my echo.proto

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

syntax="proto2";
package example;

option cc_generic_services = true;

message PutRequest {
      required string message = 1;
};

message PutResponse {
      required string message = 1;
};

message GetRequest {
      required string message = 1;
};

message GetResponse {
      required string message = 1;
};

service FileService {
      rpc put(PutRequest) returns (PutResponse);
      rpc get(GetRequest) returns (GetResponse);
};

stream1 is ok, but stream2 is always waiting for remote side;
here is my log
server side:

streaming_echo_c++ git:(master) ✗ ./build/streaming_echo_server
WARNING: Logging before InitGoogleLogging() is written to STDERR
I20250105 17:16:02.871757 123360058110400 server.cpp:1212] Server[StreamingFileService] is serving on port=8001.
I20250105 17:16:02.871828 123360058110400 server.cpp:1215] Check out http://ThinkCentre-K70:8001 in web browser.
I20250105 17:16:04.740287 123359568332480 server.cpp:90] I'm a RPC to connect stream1
I20250105 17:16:04.742151 123359882905280 server.cpp:41] Received from Stream=186: msg[0]=put: abcdefghijklmnopqrstuvwxyz
I20250105 17:16:05.742070 123359769659072 server.cpp:41] Received from Stream=186: msg[0]=put: abcdefghijklmnopqrstuvwxyz
I20250105 17:16:06.742141 123359568332480 server.cpp:41] Received from Stream=186: msg[0]=put: abcdefghijklmnopqrstuvwxyz
I20250105 17:16:07.742296 123359893391040 server.cpp:48] Stream=186 is closed
I20250105 17:16:07.742332 123359882905280 server.cpp:66] I'm a RPC to connect stream2
I20250105 17:16:07.742352 123359882905280 server.cpp:72] accept stream success
I20250105 17:16:07.742371 123359882905280 server.cpp:76] writing
I20250105 17:16:08.742444 123359882905280 server.cpp:76] writing
I20250105 17:16:09.742537 123359882905280 server.cpp:76] writing

client side:

WARNING: Logging before InitGoogleLogging() is written to STDERR
I20250105 17:16:04.731174 124031020396992 client.cpp:80] Created Stream=1
I20250105 17:16:07.842358 124030950573760 client.cpp:48] Stream=8589934593 is closed
I20250105 17:16:07.842363 124031020396992 client.cpp:111] 
I20250105 17:16:07.842392 124031020396992 client.cpp:113] waiting
I20250105 17:16:08.842461 124031020396992 client.cpp:113] waiting
I20250105 17:16:09.842549 124031020396992 client.cpp:113] waiting
I20250105 17:16:10.842635 124031020396992 client.cpp:113] waiting
I20250105 17:16:11.842722 124031020396992 client.cpp:113] waiting
I20250105 17:16:12.842808 124031020396992 client.cpp:113] waiting
I20250105 17:16:13.842920 124031020396992 client.cpp:113] waiting
I20250105 17:16:14.843019 124031020396992 client.cpp:113] waiting
I20250105 17:16:15.843068 124031020396992 client.cpp:113] waiting
^CI20250105 17:16:16.404974 124031020396992 client.cpp:118] EchoClient is going to quit