c++ - 设置套接字选项以减少 tcp 段之间的时间延迟

Question

我使用套接字将数据发送到远程。数据有效负载约为 4kB。问题是 tcp 发送的 tcp 段非常慢(每个 tcp 段延迟约 200-300 毫秒)。
我尝试了 TCP_NODELAY(启用)、TCP_QUICKACK(启用)和 TCP_CORK(禁用)，但无法减少延迟时间。
这是我的 tcpdump，每个发送的 4kB 数据分为 3 个 tcp 段:

但是，我看到其他应用程序(与同一远程通信)的 tcpdump。 tcp 段之间有很小甚至没有时间延迟。 这是我的代码:

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);
}

我的套接字设置是否不足以实现第二张图片中的 tcpdump？

Answer 1

我认为您每次发送的数据太少。尝试这个，在“void sendDataOverSocket(int clientSock)”函数中，更改发送缓冲区:int dataLen = 4*1024 + 7; ===> 到一个更大的数字。然后尝试一下。