websocket

WebSocket是一种在单个TCP连接上进行全双工通信的协议。它提供了一种在Web浏览器和服务器之间进行实时数据传输的方式。下面是一个使用C语言实现WebSocket服务器的例子：

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

#define MAX_BUFFER_SIZE 1024

// WebSocket握手请求的处理函数
void handle_handshake(int client_socket, const char* request) {
    // 解析请求头，获取WebSocket的key
    const char* key_start = strstr(request, "Sec-WebSocket-Key: ") + strlen("Sec-WebSocket-Key: ");
    const char* key_end = strstr(key_start, "\r\n");
    char key[128];
    strncpy(key, key_start, key_end - key_start);
    key[key_end - key_start] = '\0';

    // 构造响应头，进行握手
    char response[256];
    sprintf(response, "HTTP/1.1 101 Switching Protocols\r\n"
                      "Upgrade: websocket\r\n"
                      "Connection: Upgrade\r\n"
                      "Sec-WebSocket-Accept: %s\r\n\r\n", key);
    send(client_socket, response, strlen(response), 0);
}

// WebSocket消息的处理函数
void handle_message(int client_socket, const char* message) {
    // 解析消息头，获取消息长度和掩码
    int payload_length = message[1] & 0x7F;
    int mask_start = 2;
    if (payload_length == 126) {
        payload_length = (message[2] << 8) | message[3];
        mask_start = 4;
    } else if (payload_length == 127) {
        payload_length = (message[2] << 56) | (message[3] << 48) | (message[4] << 40) |
                         (message[5] << 32) | (message[6] << 24) | (message[7] << 16) |
                         (message[8] << 8) | message[9];
        mask_start = 10;
    }

    // 解析掩码，对消息进行解码
    char mask[4] = {message[mask_start], message[mask_start + 1], message[mask_start + 2], message[mask_start + 3]};
    char decoded_message[payload_length + 1];
    for (int i = 0; i < payload_length; i++) {
        decoded_message[i] = message[mask_start + 4 + i] ^ mask[i % 4];
    }
    decoded_message[payload_length] = '\0';

    // 处理解码后的消息
    printf("Received message: %s\n", decoded_message);

    // 构造响应消息，进行回复
    char response[256];
    sprintf(response, "\x81\x05Hello");
    send(client_socket, response, strlen(response), 0);
}

int main() {
    // 创建socket
    int server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket == -1) {
        perror("Failed to create socket");
        exit(EXIT_FAILURE);
    }

    // 绑定地址和端口
    struct sockaddr_in server_address;
    server_address.sin_family = AF_INET;
    server_address.sin_addr.s_addr = INADDR_ANY;
    server_address.sin_port = htons(8080);
    if (bind(server_socket, (struct sockaddr*)&server_address, sizeof(server_address)) == -1) {
        perror("Failed to bind address");
        exit(EXIT_FAILURE);
    }

    // 监听连接
    if (listen(server_socket, 5) == -1) {
        perror("Failed to listen");
        exit(EXIT_FAILURE);
    }

    printf("WebSocket server is running on port 8080...\n");

    while (1) {
        // 接受连接
        struct sockaddr_in client_address;
        socklen_t client_address_length = sizeof(client_address);
        int client_socket = accept(server_socket, (struct sockaddr*)&client_address, &client_address_length);
        if (client_socket == -1) {
            perror("Failed to accept connection");
            continue;
        }

        // 接收请求
        char request[MAX_BUFFER_SIZE];
        ssize_t request_length = recv(client_socket, request, sizeof(request), 0);
        if (request_length == -1) {
            perror("Failed to receive request");
            close(client_socket);
            continue;
        }

        // 处理握手请求
        handle_handshake(client_socket, request);

        // 接收和处理消息
        while (1) {
            char message[MAX_BUFFER_SIZE];
            ssize_t message_length = recv(client_socket, message, sizeof(message), 0);
            if (message_length == -1) {
                perror("Failed to receive message");
                break;
            } else if (message_length == 0) {
                printf("Client disconnected\n");
                break;
            }

            handle_message(client_socket, message);
        }

        // 关闭连接
        close(client_socket);
    }

    // 关闭socket
    close(server_socket);

    return 0;
}

这个例子展示了一个简单的WebSocket服务器的实现，它使用C语言编写，并使用了HTTP解析器、SHA1算法和WebSocket解析器。你可以将这个例子在Visual Studio中修改并在Linux下运行。