Fix WebSocket sendFrame delay by enabling TCP_NODELAY

[Copilot]

WebSocket sendFrame() experiences ~2 second delays because Nagle's algorithm buffers small frames. While client-side WebSockets inherit TCP_NODELAY from HTTPClientSession, server-side WebSockets created from HTTPServerRequest do not.

Changes

• WebSocketImpl.cpp: Enable TCP_NODELAY in constructor for all WebSocket connections

  • Skip Unix domain sockets which don't support TCP options
  • Gracefully handle socket configuration errors

• WebSocket.h: Document TCP_NODELAY behavior

Implementation

// WebSocketImpl constructor now sets TCP_NODELAY
try
{
    if (_pStreamSocketImpl->address().family() != SocketAddress::UNIX_LOCAL)
        _pStreamSocketImpl->setNoDelay(true);
}
catch (NetException&) { /* ignore */ }
catch (Poco::Exception&) { /* ignore */ }

This eliminates the artificial delays caused by Nagle's algorithm buffering small WebSocket frames, making frame sends immediate regardless of whether the WebSocket originated from a client or server connection.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• 192.168.168.192
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest /tmp/ccsAxjaq.s ork/�� ch=" --green --p-I -I nit/include -I k/poco/poco/Net/-I t.cpp.o -D_LARGEFILE64_-I -qui�� /bin/c++ -DPOCO_-I /home/REDACTED/wor/home/REDACTED/work/poco/poco/CppUnit/include nit/include /home/REDACTED/woras -I /home/REDACTED/wor/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (packet block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest CMakeFiles/Net.dir/src/WebSocketImpl.cpp.d -MF t/testsuite/all -MT Net/CMakeFiles/Net.dir/src/WebSocketImpl.cpp.o -D_GNU_SOURCE -D Net_EXPORTS -D -DPO�� cpp.o -DPOCO_ENABLE_CPP20 dation/include _FD_EPOLL -DPOCOas nit/include -D_FILE_OFFSET_B/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (packet block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest FFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_REENTRAN -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_OS_FAMILYbash nit/include -DUTF8PROC_STATI--noprofile FFSET_BITS=64 -D_LARGEFILE64_SOU872727f6db7dcd22990d7845dae167444594bf63 -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_HAVE_SEND/bin/sh nit/include -DUTF8PROC_STATIcd /home/REDACTED/work/poco/poco/cmake-build && /usr/local/bin/cmake -E cmake_depends "Unix Makefiles" /home/REDACTED/work/poco/poco /home/REDACTED/work/poco/poco/Foundation /home/REDACTED/work/poco/poco/cmake-build /home/REDACTED/work/poco/poco/cmak e-build/Foundat (packet block)
• 239.255.1.2
  • Triggering command: REDACTED, pid is -1 (packet block)
• 255.255.255.255
  • Triggering command: REDACTED, pid is -1 (packet block)
• 86.195.122.80.in-addr.arpa
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest /tmp/ccsAxjaq.s ork/�� ch=" --green --p-I -I nit/include -I k/poco/poco/Net/-I t.cpp.o -D_LARGEFILE64_-I -qui�� /bin/c++ -DPOCO_-I /home/REDACTED/wor/home/REDACTED/work/poco/poco/CppUnit/include nit/include /home/REDACTED/woras -I /home/REDACTED/wor/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest CMakeFiles/Net.dir/src/WebSocketImpl.cpp.d -MF t/testsuite/all -MT Net/CMakeFiles/Net.dir/src/WebSocketImpl.cpp.o -D_GNU_SOURCE -D Net_EXPORTS -D -DPO�� cpp.o -DPOCO_ENABLE_CPP20 dation/include _FD_EPOLL -DPOCOas nit/include -D_FILE_OFFSET_B/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest FFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_REENTRAN -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_OS_FAMILYbash nit/include -DUTF8PROC_STATI--noprofile FFSET_BITS=64 -D_LARGEFILE64_SOU872727f6db7dcd22990d7845dae167444594bf63 -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_HAVE_SEND/bin/sh nit/include -DUTF8PROC_STATIcd /home/REDACTED/work/poco/poco/cmake-build && /usr/local/bin/cmake -E cmake_depends "Unix Makefiles" /home/REDACTED/work/poco/poco /home/REDACTED/work/poco/poco/Foundation /home/REDACTED/work/poco/poco/cmake-build /home/REDACTED/work/poco/poco/cmak e-build/Foundat (dns block)
• aliastest.pocoproject.org
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest /tmp/ccsAxjaq.s ork/�� ch=" --green --p-I -I nit/include -I k/poco/poco/Net/-I t.cpp.o -D_LARGEFILE64_-I -qui�� /bin/c++ -DPOCO_-I /home/REDACTED/wor/home/REDACTED/work/poco/poco/CppUnit/include nit/include /home/REDACTED/woras -I /home/REDACTED/wor/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest CMakeFiles/Net.dir/src/WebSocketImpl.cpp.d -MF t/testsuite/all -MT Net/CMakeFiles/Net.dir/src/WebSocketImpl.cpp.o -D_GNU_SOURCE -D Net_EXPORTS -D -DPO�� cpp.o -DPOCO_ENABLE_CPP20 dation/include _FD_EPOLL -DPOCOas nit/include -D_FILE_OFFSET_B/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest FFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_REENTRAN -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_OS_FAMILYbash nit/include -DUTF8PROC_STATI--noprofile FFSET_BITS=64 -D_LARGEFILE64_SOU872727f6db7dcd22990d7845dae167444594bf63 -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_HAVE_SEND/bin/sh nit/include -DUTF8PROC_STATIcd /home/REDACTED/work/poco/poco/cmake-build && /usr/local/bin/cmake -E cmake_depends "Unix Makefiles" /home/REDACTED/work/poco/poco /home/REDACTED/work/poco/poco/Foundation /home/REDACTED/work/poco/poco/cmake-build /home/REDACTED/work/poco/poco/cmak e-build/Foundat (dns block)
• pocoproject.org
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest /tmp/ccsAxjaq.s ork/�� ch=" --green --p-I -I nit/include -I k/poco/poco/Net/-I t.cpp.o -D_LARGEFILE64_-I -qui�� /bin/c++ -DPOCO_-I /home/REDACTED/wor/home/REDACTED/work/poco/poco/CppUnit/include nit/include /home/REDACTED/woras -I /home/REDACTED/wor/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest CMakeFiles/Net.dir/src/WebSocketImpl.cpp.d -MF t/testsuite/all -MT Net/CMakeFiles/Net.dir/src/WebSocketImpl.cpp.o -D_GNU_SOURCE -D Net_EXPORTS -D -DPO�� cpp.o -DPOCO_ENABLE_CPP20 dation/include _FD_EPOLL -DPOCOas nit/include -D_FILE_OFFSET_B/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest FFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_REENTRAN -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_OS_FAMILYbash nit/include -DUTF8PROC_STATI--noprofile FFSET_BITS=64 -D_LARGEFILE64_SOU872727f6db7dcd22990d7845dae167444594bf63 -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_HAVE_SEND/bin/sh nit/include -DUTF8PROC_STATIcd /home/REDACTED/work/poco/poco/cmake-build && /usr/local/bin/cmake -E cmake_depends "Unix Makefiles" /home/REDACTED/work/poco/poco /home/REDACTED/work/poco/poco/Foundation /home/REDACTED/work/poco/poco/cmake-build /home/REDACTED/work/poco/poco/cmak e-build/Foundat (dns block)
• pool.ntp.org
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest /tmp/ccsAxjaq.s ork/�� ch=" --green --p-I -I nit/include -I k/poco/poco/Net/-I t.cpp.o -D_LARGEFILE64_-I -qui�� /bin/c++ -DPOCO_-I /home/REDACTED/wor/home/REDACTED/work/poco/poco/CppUnit/include nit/include /home/REDACTED/woras -I /home/REDACTED/wor/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest CMakeFiles/Net.dir/src/WebSocketImpl.cpp.d -MF t/testsuite/all -MT Net/CMakeFiles/Net.dir/src/WebSocketImpl.cpp.o -D_GNU_SOURCE -D Net_EXPORTS -D -DPO�� cpp.o -DPOCO_ENABLE_CPP20 dation/include _FD_EPOLL -DPOCOas nit/include -D_FILE_OFFSET_B/home/REDACTED/work/poco/poco/Net/include FFSET_BITS=64 -D-I (dns block)
  • Triggering command: ./bin/Net-testREDACTED ./bin/Net-testREDACTED -all WebSocketTest FFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_REENTRAN -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_OS_FAMILYbash nit/include -DUTF8PROC_STATI--noprofile FFSET_BITS=64 -D_LARGEFILE64_SOU872727f6db7dcd22990d7845dae167444594bf63 -DPO�� include -DPOCO_ENABLE_CPP20 dation/include -DPOCO_HAVE_SEND/bin/sh nit/include -DUTF8PROC_STATIcd /home/REDACTED/work/poco/poco/cmake-build && /usr/local/bin/cmake -E cmake_depends "Unix Makefiles" /home/REDACTED/work/poco/poco /home/REDACTED/work/poco/poco/Foundation /home/REDACTED/work/poco/poco/cmake-build /home/REDACTED/work/poco/poco/cmak e-build/Foundat (dns block)

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>WebSocket sendFrame Delay and ReceiveTimeout Dependency - Need Help</issue_title>
<issue_description>Hi,
I'm having a problem with Poco::Net::WebSocket.sendFrame(). It takes forever (about 2 seconds) to execute in a non-blocking context. It seems that sendFrame() only works when a receive timeout happens, which makes the receiving end laggy and timeouty. I tried setting the WebSocket to non-blocking mode with ws->setBlocking(false), but that didn't help. If I set ws->setReceiveTimeout(Poco::Timespan(0, 1000)), the receive timeout keeps getting called, and sendFrame() doesn't lag at all.

What am I missing? Should I set the timeout low, catch it, and then ignore it? I'd appreciate any help or suggestions.
I've attached a sample code below.

#include <chrono>
#include <iostream>
#include <thread>

#include "Poco/Net/HTTPRequest.h"
#include "Poco/Net/HTTPResponse.h"
#include "Poco/Net/HTTPSClientSession.h"
#include "Poco/Net/SSLManager.h"
#include "Poco/Net/WebSocket.h"

class WebSocketClient {
   private:
    Poco::Net::WebSocket* ws;
    std::thread receiveThread;
    std::atomic<bool> running{true};

   public:
    WebSocketClient(const std::string& host, uint16_t port, const std::string& path) {
        Poco::Net::Context::Ptr context = new Poco::Net::Context(
            Poco::Net::Context::CLIENT_USE, "", "", "", Poco::Net::Context::VERIFY_NONE, 9, false,
            "ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH");

        Poco::Net::HTTPSClientSession session(host, port, context);
        session.setTimeout(Poco::Timespan(5, 0)); 
        Poco::Net::HTTPRequest request(Poco::Net::HTTPRequest::HTTP_GET, path,
                                       Poco::Net::HTTPMessage::HTTP_1_1);
        Poco::Net::HTTPResponse response;

        ws = new Poco::Net::WebSocket(session, request, response);
        // ws->setReceiveTimeout(Poco::Timespan(0, 1000)); 
        receiveThread = std::thread(&WebSocketClient::receiveLoop, this);
    }

    ~WebSocketClient() {
        running = false;
        if (receiveThread.joinable()) {
            receiveThread.join();
        }
        delete ws;
    }

    bool sendMessage(const std::string& message) {
        try {
            auto start = std::chrono::steady_clock::now();

            int flags = Poco::Net::WebSocket::FRAME_TEXT;
            int sent = ws->sendFrame(message.data(), message.length(), flags);

            auto end = std::chrono::steady_clock::now();
            auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);

            std::cout << "Time taken for sendFrame: " << duration.count() << " ms\n";

            return sent == message.length();
        } catch (const Poco::TimeoutException& e) {
            std::cerr << "Timeout sending message: " << e.what() << std::endl;
            return false;
        } catch (const Poco::Exception& e) {
            std::cerr << "Error sending message: " << e.what() << std::endl;
            return false;
        }
    }

   private:
    void receiveLoop() {
        const int BUFFER_SIZE = 1024;
        char buffer[BUFFER_SIZE];
        int flags = 0;

        while (running) {
            try {
                int received = ws->receiveFrame(buffer, sizeof(buffer), flags);
                if (received > 0) {
                    std::string message(buffer, received);
                    std::cout << "Received message: " << message << std::endl;
                }
            } catch (const Poco::TimeoutException&) {
                std::cerr << "Timeout receiving message\n";
                std::this_thread::sleep_for(std::chrono::milliseconds(100));
                continue;
            } catch (const Poco::Exception& e) {
                std::cerr << "Error in receive loop: " << e.what() << std::endl;
                break;
            }
        }
    }
};

int main() {
    try {
        WebSocketClient client("echo.websocket.org", 443, "/");

        while (true) {
            std::cout << "Sending message: test\n";
            client.sendMessage("test");
            std::this_thread::sleep_for(std::chrono::seconds(3));
        }
    } catch (const Poco::Exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
        return 1;
    }
    return 0;
}```

</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes WebSocket sendFrame Delay and ReceiveTimeout Dependency - Need Help #4756

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