Setting socket options to reduce time delay between tcp segments - c++

Question

Im using socket to send data to remote. The data payload is ~4kB. Problem is tcp segments sent by tcp so slow (delay ~200-300ms each tcp segments).
I tried with TCP_NODELAY (enabled), TCP_QUICKACK (enabled) and TCP_CORK(disabled) but cannot reduce the delayed time.
Here is my tcpdump, each 4kB data sent is divided into 3 tcp segments:
However, I saw a tcpdump by other application (which communicate with same remote). There is a very small or even no time delay between tcp segments.
Here is my code:
void createServerSocket() {
int serverSockFd = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP);
std::string address = "fd53:7cb8:383:5::73";
int port = 42519;
if (serverSockFd < 0)
{
printf("Create Server socket fail");
return;
}
struct sockaddr_in6 serverAddress;
(void)memset(&serverAddress, 0, sizeof(sockaddr_in6));
serverAddress.sin6_family = AF_INET6;
serverAddress.sin6_port = htons(port);
int result = inet_pton(AF_INET6, address.c_str(), &serverAddress.sin6_addr);
if (result <= 0)
{
printf("inet_pton() failed portnumber: %d, address: %s \n", port, address.c_str());
return;
}
// setting socket options
int flag = 1;
if(setsockopt(serverSockFd,IPPROTO_TCP,TCP_QUICKACK ,(char *)&flag,sizeof(flag)) == -1)
{
printf("setsockopt TCP_QUICKACK failed for server socket on address %s \n", address.c_str());
}
if(setsockopt(serverSockFd,IPPROTO_TCP,TCP_CORK,(char *)&flag,sizeof(flag)) == -1)
{
printf("setsockopt TCP_CORK failed for server socket on address %s \n", address.c_str());
}
if(setsockopt(serverSockFd,IPPROTO_TCP,TCP_NODELAY,(char *)&flag,sizeof(flag)) == -1)
{
printf("setsockopt TCP_NODELAY failed for server socket on address %s \n", address.c_str());
}
result = bind(serverSockFd, (struct sockaddr*)&serverAddress, sizeof(sockaddr_in6));
if (result != 0)
{
printf("bind() failed portnumber: %d, address: %s \n", port, address.c_str());
return ;
}
result = listen(serverSockFd, 10);
if (result != 0) {
printf("listen() failed portnumber: %d, address: %s \n", port, address.c_str());
return ;
}
acceptConnect(serverSockFd);
}
void acceptConnect(int serverSock)
{
struct sockaddr_in6 clientAddress;
socklen_t len = sizeof(sockaddr_in6);
memset(&clientAddress, 0, sizeof(sockaddr_in6));
const int clientSocket = accept(serverSock, (struct sockaddr*)&clientAddress, &len);
if(clientSocket >= 0) {
char str_addr[INET6_ADDRSTRLEN];
inet_ntop(AF_INET6, &(clientAddress.sin6_addr),
str_addr, sizeof(str_addr));
printf("New connection from: %s:%d ...\n", str_addr, ntohs(clientAddress.sin6_port));
receiveDataFromSocket(clientSocket);
}
}
void receiveDataFromSocket(int socket)
{
int SOCKET_BUFFER_MAX_SIZE = 8*1024;
char buffer[SOCKET_BUFFER_MAX_SIZE];
memset(buffer, '\0', SOCKET_BUFFER_MAX_SIZE);
//Receive data from sock
while (true) {
int dataLen = recv(socket, buffer, SOCKET_BUFFER_MAX_SIZE, 0);
printf("Receive data from socket: %d, msgLength = %d\n", socket, dataLen);
sendDataOverSocket(socket);
}
}
void sendDataOverSocket(int clientSock)
{
int dataLen = 4*1024 + 7;
char *buf = new char[dataLen];
memset(buf, 'a', 4*1024 + 7);
int ret;
ret = send(clientSock, buf, dataLen, 0);
if (ret <= 0) {
printf("ERROR Send message over socket");
return;
}
int error_code;
socklen_t error_code_size = sizeof(sockaddr_in6);
getsockopt(clientSock, SOL_SOCKET, SO_ERROR, &error_code, &error_code_size);
printf("Error code size: %d, error code: %d\n", error_code_size, error_code);
}
Does my socket not setting enough to achive tcpdump in second picture?

Answer 1

I thing you are sending too few data evey time.
trying this , in "void sendDataOverSocket(int clientSock)" function, change the sending buffer:
int dataLen = 4*1024 + 7; ===> to a bigger number.
then try it.