c++ - Bug 保活延迟

Question

这段代码使用 keep-alive 连接来加载许多共享相同 IP 地址的域，但是在前 25 个域之后有一个错误，每个域加载都有 30 秒的延迟!如何解决？

#pragma comment(lib,"ws2_32.lib")
#include <WinSock2.h>
#include <iostream>
int main(){
    WSAData wsaData;
    WORD DllVersion = MAKEWORD(2, 1);
    if (WSAStartup(DllVersion, &wsaData) != 0) {
        MessageBoxA(NULL, "Winsock startup failed", "Error", MB_OK | MB_ICONERROR);
        exit(1);
    }
    SOCKADDR_IN addr;
    int sizeofaddr = sizeof(addr);
    addr.sin_addr.s_addr = inet_addr("123.123.123.123");
    addr.sin_port = htons(80);
    addr.sin_family = AF_INET;
    SOCKET Connection = socket(AF_INET, SOCK_STREAM, NULL);
    if (connect(Connection, (SOCKADDR*)&addr, sizeofaddr) != 0)
    {
        MessageBoxA(NULL, "Failed to Connect", "Error", MB_OK | MB_ICONERROR);
        return 0;
    }
    std::cout << "Connected!" << std::endl;
    char MTD[] = "GET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:keep-alive\r\n\r\nGET / HTTP/1.1\r\nHost:site.com\r\nConnection:close\r\n\r\n";
    send(Connection, MTD, sizeof(MTD), NULL);
    char MOTD[1];
    int result;
    while ((result = recv(Connection, MOTD, 1, NULL)) > 0){
        std::cout << MOTD[0]; // ...
    }
    if (result == 0) {
        // end of stream
        std::cout << "end of stream";
        close(Connection);
    } else if (result < 0) {
        // error
        std::cout << "error";
        perror("recv"); // at least
        close(Connection);
    } else {
        std::cout << "data received";
        // data received, in MOTD[0..result-1]
    }
};

Answer 1

result=recv(Connection, MOTD, 1, NULL);
while(recv(Connection, MOTD, 1, NULL)){

这毫无意义。第一个 recv() 将至少一个字节读入缓冲区或将 result 设置为零或 -1，因此您立即忽略它所做的一切并发出另一个 recv ()，您忽略其结果。它应该更像这样:

while ((result = recv(Connection, MOTD, 1, NULL)) > 0){
    // data received, in MOTD[0..result-1]
}
if (result == 0) {
    // end of stream
    close(Connection);
} else if (result < 0) {
    // error
    perror("recv"); // at least
    close(Connection);
}

注意您根本没有使用 HTTP keepalive。您正在为每个请求创建一个新套接字并且永远不会关闭它，至少在您使用此答案中的代码之前是这样。您还通过Connection: keepalive header 告诉服务器保持该连接有效，这只会浪费服务器资源。要么正确使用 HTTP keep-alive，要么在每次请求后关闭套接字。