使用C语言发送http请求的demo

以下是一个使用C语言发送HTTP请求的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>

#define MAX_BUFFER_SIZE 1024

int main(int argc, char *argv[]) {

    struct sockaddr_in server_addr;
    struct hostent *server;
    int socket_fd, port_number, bytes, sent, received, total;
    char buffer[MAX_BUFFER_SIZE], request[MAX_BUFFER_SIZE];

    if (argc < 3) {
        fprintf(stderr, "Usage: %s <hostname> <port_number> <path>\n", argv[0]);
        exit(1);
    }

    port_number = atoi(argv[2]);

    /* 创建 socket */
    socket_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (socket_fd < 0) {
        perror("Failed to create socket");
        exit(1);
    }

    /* 获取服务器信息 */
    server = gethostbyname(argv[1]);
    if (server == NULL) {
        fprintf(stderr, "Failed to get host by name");
        exit(1);
    }

    /* 初始化服务器地址结构 */
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port_number);
    memcpy(&server_addr.sin_addr.s_addr, server->h_addr, server->h_length);

    /* 连接服务器 */
    if (connect(socket_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("Failed to connect to server");
        exit(1);
    }

    /* 构造 HTTP 请求 */
    sprintf(request, "GET %s HTTP/1.1\r\nHost: %s:%d\r\nConnection: close\r\n\r\n", argv[3], argv[1], port_number);

    /* 发送 HTTP 请求 */
    total = strlen(request);
    sent = 0;
    do {
        bytes = write(socket_fd, request + sent, total - sent);
        if (bytes < 0) {
            perror("Failed to send request");
            exit(1);
        }
        if (bytes == 0) {
            break;
        }
        sent += bytes;
    } while (sent < total);

    /* 接收 HTTP 响应 */
    memset(buffer, 0, sizeof(buffer));
    received = 0;
    do {
        bytes = read(socket_fd, buffer + received, MAX_BUFFER_SIZE - received);
        if (bytes < 0) {
            perror("Failed to receive response");
            exit(1);
        }
        if (bytes == 0) {
            break;
        }
        received += bytes;
    } while (received < MAX_BUFFER_SIZE);

    /* 输出 HTTP 响应 */
    printf("%s\n", buffer);

    /* 关闭 socket */
    close(socket_fd);

    return 0;
}

你可以将以上代码保存到一个名为 `http_request.c` 的文件中，并使用以下命令编译：

gcc http_request.c -o http_request

然后在终端中运行以下命令来发送 HTTP 请求：

./http_request example.com 80 /

其中，`example.com` 是要请求的网站的域名，`80` 是要连接的端口号，`/` 是要请求的路径。你可以根据需要修改这些参数。