websocket客户端C语言代码

以下是一个简单的C语言websocket客户端代码，实现了与服务器建立websocket连接，并发送和接收消息。

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

#define BUFSIZE 1024

int main(int argc, char **argv) {
    if (argc != 2) {
        printf("Usage: %s <websocket server address>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    char *address = argv[1];
    int port = 80;
    char *path = "/";
    char url[BUFSIZE];
    snprintf(url, BUFSIZE, "GET %s HTTP/1.1\r\n"
                            "Host: %s:%d\r\n"
                            "Connection: Upgrade\r\n"
                            "Upgrade: websocket\r\n"
                            "Sec-WebSocket-Version: 13\r\n"
                            "\r\n", path, address, port);
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    struct sockaddr_in serv_addr;
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(address);
    serv_addr.sin_port = htons(port);
    if (connect(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
        perror("connect");
        exit(EXIT_FAILURE);
    }
    if (send(sockfd, url, strlen(url), 0) < 0) {
        perror("send");
        exit(EXIT_FAILURE);
    }
    char buf[BUFSIZE];
    ssize_t n;
    char *p;
    if ((p = strstr(buf, "\r\n\r\n")) == NULL) {
        printf("Error: cannot find \\r\\n\\r\\n in response\n");
        exit(EXIT_FAILURE);
    }
    p += 4;
    while ((n = read(sockfd, buf, BUFSIZE)) > 0) {
        // parse websocket message here
        // ...
    }
    close(sockfd);
    return 0;
}

需要注意的是，websocket通信需要对消息进行打包和解包，具体实现较为复杂，这里只实现了基本的建立连接和发送、接收消息的功能。完整的websocket客户端实现可参考开源库，比如libwebsockets。