c - 使用c进行套接字编程时连接到远程服务器时出错

Question

这是一个示例代码，我尝试将请求传递到服务器并获取所需的数据。但是我连接到远程服务器的代码没有像我想象的那样工作。

if (connect(s , (struct sockaddr *)&server , sizeof(server)) < 0)
{
    puts("connect error");
    return 1;
}

puts("Connected");

我不知道为什么条件值低于零。为什么连接没有完成？

完整代码:

    /*
    Create a TCP socket
*/

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

#pragma comment(lib,"ws2_32.lib") //Winsock Library

int main(int argc , char *argv[])
{
    WSADATA wsa;
    SOCKET s;
    struct sockaddr_in server;
    char *message , server_reply[2000];
    int recv_size;

    printf("\nInitialising Winsock...");
    if (WSAStartup(MAKEWORD(2,2),&wsa) != 0)
    {
        printf("Failed. Error Code : %d",WSAGetLastError());
        return 1;
    }

    printf("Initialised.\n");

    //Create a socket
    if((s = socket(AF_INET , SOCK_STREAM , 0 )) == INVALID_SOCKET)
    {
        printf("Could not create socket : %d" , WSAGetLastError());
    }

    printf("Socket created.\n");


    server.sin_addr.s_addr = inet_addr("74.125.235.20");
    server.sin_family = AF_INET;
    server.sin_port = htons( 80 );

    //Connect to remote server
    if (connect(s , (struct sockaddr *)&server , sizeof(server)) < 0)
    {
        puts("connect error");
        return 1;
    }

    puts("Connected");

    //Send some data
    message = "GET / HTTP/1.1\r\n\r\n";
    if( send(s , message , strlen(message) , 0) < 0)
    {
        puts("Send failed");
        return 1;
    }
    puts("Data Send\n");

    //Receive a reply from the server
    if((recv_size = recv(s , server_reply , 2000 , 0)) == SOCKET_ERROR)
    {
        puts("recv failed");
    }

    puts("Reply received\n");

    //Add a NULL terminating character to make it a proper string before printing
    server_reply[recv_size] = '\0';
    puts(server_reply);
    closesocket(s);
    WSACleanup();

    return 0;
}

Answer 1

在分配之前，您需要将整个 sockaddr_in 初始化为零。

memset( &server, 0, sizeof(server) );
server.sin_addr.s_addr = inet_addr("74.125.235.20");
server.sin_family = AF_INET;
server.sin_port = htons( 80 );

我复制了你的代码并尝试了一下，它似乎有效，也许你有防火墙干扰。

顺便说一句，我将您的 inet_addr 调用更改为

InetPtonA( AF_INET, "74.125.235.20", &server.sin_addr.s_addr );