Use tcp_nodelay on socket server (#537)

The sockets we use in this library should be optimized for real-time
communication, not for throughput. Therefore, they should use
tcp_nodelay by default.

Author: urfeex

include/ur_client_library/comm/socket_t.h

@@ -71,6 +71,8 @@ typedef int socket_t;
 #  define MSG_NOSIGNAL 0
 #endif
 
+#include "ur_client_library/log.h"
+
 /*!
  * \brief Get the last socket error as an std::error_code
  *
@@ -92,3 +94,14 @@ inline std::system_error makeSocketError(const std::string& message)
 {
   return std::system_error(getLastSocketErrorCode(), message);
 }
+
+inline void setSocketOptionAndWarnOnError(socket_t socket, int level, int optname, const void* optval,
+                                          unsigned int optlen, const std::string& option_name)
+{
+  int result = ur_setsockopt(socket, level, optname, optval, optlen);
+  if (result != 0)
+  {
+    std::error_code error_code = getLastSocketErrorCode();
+    URCL_LOG_WARN("Failed to set socket option %s: %s", option_name.c_str(), error_code.message().c_str());
+  }
+}

src/comm/tcp_server.cpp

@@ -26,6 +26,9 @@
  */
 //----------------------------------------------------------------------
 
+#ifndef _WIN32
+#  include <netinet/tcp.h>
+#endif
 #include <ur_client_library/log.h>
 #include <ur_client_library/comm/tcp_server.h>
 
@@ -67,11 +70,11 @@ void TCPServer::init()
   {
     throw makeSocketError("Failed to create socket endpoint");
   }
-  int flag = 1;
+  constexpr int flag = 1;
 #ifndef _WIN32
-  ur_setsockopt(listen_fd_, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(int));
+  setSocketOptionAndWarnOnError(listen_fd_, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag), "SO_REUSEADDR");
 #endif
-  ur_setsockopt(listen_fd_, SOL_SOCKET, SO_KEEPALIVE, &flag, sizeof(int));
+  setSocketOptionAndWarnOnError(listen_fd_, SOL_SOCKET, SO_KEEPALIVE, &flag, sizeof(flag), "SO_KEEPALIVE");
 
   URCL_LOG_DEBUG("Created socket with FD %d", (int)listen_fd_);
 
@@ -257,6 +260,13 @@ void TCPServer::handleConnect()
       ur_close(client_fd);
     }
   }
+
+  if (accepted)
+  {
+    constexpr int flag = 1;
+    setSocketOptionAndWarnOnError(client_fd, IPPROTO_TCP, TCP_NODELAY, &flag, sizeof(flag), "TCP_NODELAY");
+  }
+
   {
     std::lock_guard<std::mutex> lk(callback_mutex_);
     if (new_connection_callback_ && accepted)

src/comm/tcp_socket.cpp

@@ -24,6 +24,7 @@
 #include <cstring>
 #include <sstream>
 #include <thread>
+#include "ur_client_library/comm/socket_t.h"
 
 #ifndef _WIN32
 #  include <arpa/inet.h>
@@ -52,22 +53,23 @@ TCPSocket::~TCPSocket()
 
 void TCPSocket::setupOptions()
 {
-  int flag = 1;
-  ur_setsockopt(socket_fd_, IPPROTO_TCP, TCP_NODELAY, &flag, sizeof(int));
+  constexpr int flag = 1;
+  setSocketOptionAndWarnOnError(socket_fd_, IPPROTO_TCP, TCP_NODELAY, &flag, sizeof(flag), "TCP_NODELAY");
 
   // macOS does not have TCP_QUICKACK
 #ifdef TCP_QUICKACK
-  ur_setsockopt(socket_fd_, IPPROTO_TCP, TCP_QUICKACK, &flag, sizeof(int));
+  setSocketOptionAndWarnOnError(socket_fd_, IPPROTO_TCP, TCP_QUICKACK, &flag, sizeof(flag), "TCP_QUICKACK");
 #endif
 
   if (recv_timeout_ != nullptr)
   {
 #ifdef _WIN32
     DWORD value = recv_timeout_->tv_sec * 1000;
     value += recv_timeout_->tv_usec / 1000;
-    ur_setsockopt(socket_fd_, SOL_SOCKET, SO_RCVTIMEO, &value, sizeof(value));
+    setSocketOptionAndWarnOnError(socket_fd_, SOL_SOCKET, SO_RCVTIMEO, &value, sizeof(value), "SO_RCVTIMEO");
 #else
-    ur_setsockopt(socket_fd_, SOL_SOCKET, SO_RCVTIMEO, recv_timeout_.get(), sizeof(timeval));
+    setSocketOptionAndWarnOnError(socket_fd_, SOL_SOCKET, SO_RCVTIMEO, recv_timeout_.get(), sizeof(timeval),
+                                  "SO_RCVTIMEO");
 #endif
   }
 }