winsock2 中的连接方法似乎不起作用

Question

#define PORT 3000

int sock()
{
    int valread;
    struct sockaddr_in serv_addr;
    const char* hello = "Hello from client";
    char buffer[1024] = { 0 };
    SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock < 0)
    {
        printf("\n Socket creation error \n");
        return -1;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);

    // Convert IPv4 and IPv6 addresses from text to binary form 
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0)
    {
        printf("\nInvalid address/ Address not supported \n");
        return -1;
    }

    if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0)
    {
        printf("\nConnection Failed \n");
        return -1;
    }
    send(sock, hello, strlen(hello), 0);
    printf("Hello message sent\n");

    return 0;
}

我有这个套接字代码，要在 localhost:3000 地址发送。但是它们没有发送，并且弹出连接失败错误。我在该端口打开了 node.js 服务器侦听器套接字。

Answer 1

仅在 Windows ¹ 上，您必须调用 WSAStartup() 来初始化 Winsock 库之前使用任何其他套接字函数，如 connect()。见Initializing Winsock。使用完 Winsock 后，您应该致电 WSACleanup()。

^{1：在非Windows平台上，使用套接字时没有等效的启动/清理函数需要调用。}

试试这样的：

#include <winsock2.h>
#include <windows.h>
#include <stdio.h>

#define PORT 3000

int main()
{
    WSADATA wsa;
    int iResult = WSAStartup(MAKEWORD(2,0), &wsa);
    if (iResult != 0)
    {
        printf("WSAStartup failed: %d\n", iResult);
        return INVALID_SOCKET;
    }

    printf("Winsock initialized\n");

    struct sockaddr_in serv_addr;
    ZeroMemory(&serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);

    // Convert IPv4 and IPv6 addresses from text to binary form 
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0)
    {
        printf("Invalid address/ Address not supported \n");
        WSACleanup();
        return -1;
    }

    SOCKET sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock == INVALID_SOCKET)
    {
        printf("Socket creation failed: %d\n", WSAGetLastError());
        WSACleanup();
        return -1;
    }

    if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == SOCKET_ERROR)
    {
        printf("Connection failed: %d\n", WSAGetLastError());
        closesocket(sock);
        WSACleanup();
        return -1;
    }

    printf("Connection successful\n");

    const char* hello = "Hello from client";

    if (send(sock, hello, strlen(hello), 0) == SOCKET_ERROR)
    {
        printf("Send failed: %d\n", WSAGetLastError());
        closesocket(sock);
        WSACleanup();
        return -1;
    }

    printf("Hello message sent\n");

    closesocket(sock);
    WSACleanup();

    return 0;
}

也就是说，您确实应该使用getaddrinfo() 而不是inet_pton()，尤其是如果您想同时支持 IPv4 和 IPv6，例如：

#include <winsock2.h>
#include <ws2tcpip.h>
#include <windows.h>
#include <stdio.h>

#define PORT "3000"

int main()
{
    WSADATA wsa;
    int iResult = WSAStartup(MAKEWORD(2,0), &wsa);
    if (iResult != 0)
    {
        printf("WSAStartup failed: %d\n", iResult);
        return INVALID_SOCKET;
    }

    printf("Winsock initialized\n");

    struct addrinfo hints, *addrs;
    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    // Convert IPv4 and IPv6 addresses from text to binary form 
    iResult = getaddrinfo("127.0.0.1", PORT, &hints, &addrs);
    if (iResult != 0)
    {
        printf("Get Address Info failed: (%d) %s\n", iResult, gai_strerror(iResult));
        WSACleanup();
        return -1;
    }

    SOCKET sock = INVALID_SOCKET;

    for(struct addrinfo *addr = addrs; addr != NULL; addr = addr->ai_next)
    {
        sock = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
        if (sock != INVALID_SOCKET)
        {
            if (connect(sock, addr->ai_addr, addr->ai_addrlen) != SOCKET_ERROR)
                break;

            closesocket(sock);
            sock = INVALID_SOCKET;
        }
    }

    if (sock == INVALID_SOCKET)
    {
        printf("Socket creation failed/Connection failed\n");
        WSACleanup();
        return -1;
    }

    printf("Connection successful\n");

    const char* hello = "Hello from client";

    if (send(sock, hello, strlen(hello), 0) == SOCKET_ERROR)
    {
        printf("Send failed: %d\n", WSAGetLastError());
        closesocket(sock);
        WSACleanup();
        return -1;
    }

    printf("Hello message sent\n");

    closesocket(sock);
    WSACleanup();

    return 0;
}