用c++构建 WebSocket 数据帧回送给客户端-Go服务器开发

以下是一个简单的示例代码，用于构建 WebSocket 数据帧并将其发送回客户端：

#include <iostream>
#include <cstring>
using namespace std;
enum Opcode {
    CONTINUATION_FRAME = 0x00,
    TEXT_FRAME = 0x01,
    BINARY_FRAME = 0x02,
    CONNECTION_CLOSE = 0x08,
    PING_FRAME = 0x09,
    PONG_FRAME = 0x0A
};
enum CloseCode {
    NORMAL_CLOSURE = 1000,
    ENDPOINT_GOING_AWAY = 1001,
    PROTOCOL_ERROR = 1002,
    UNSUPPORTED_DATA = 1003,
    NO_STATUS_RCVD = 1005,
    ABNORMAL_CLOSURE = 1006,
    INVALID_PAYLOAD = 1007,
    POLICY_VIOLATION = 1008,
    MESSAGE_TOO_BIG = 1009,
    MANDATORY_EXT = 1010,
    INTERNAL_SERVER_ERR = 1011,
    TLS_HANDSHAKE = 1015
};
struct WebSocketFrame {
    unsigned char fin;
    unsigned char opcode;
    unsigned char mask;
    unsigned char payload_len;
    unsigned char masking_key[4];
    unsigned char *payload_data;
};
void sendWebSocketData(int sockfd, const char* data, int length, Opcode opcode) {
    WebSocketFrame frame;
    memset(&frame, 0, sizeof(frame));
    
    frame.fin = 1;
    frame.opcode = opcode;
    frame.mask = 0; // server to client doesn't need masking
    
    if(length <= 125) {
        frame.payload_len = length;
    } else if(length <= 65535) {
        frame.payload_len = 126;
        unsigned short len = htons(length);
        memcpy(frame.payload_data, &len, sizeof(len));
    } else {
        frame.payload_len = 127;
        unsigned long long len = htobe64(length);
        memcpy(frame.payload_data, &len, sizeof(len));
    }
    
    // allocate memory for the frame
    int frame_size = sizeof(unsigned char) * (2 + (frame.payload_len > 125 ? (frame.payload_len == 126 ? 2 : 8) : 0)) + length;
    unsigned char* frame_data = new unsigned char[frame_size];
    
    memset(frame_data, 0, frame_size);
    frame_data[0] |= frame.fin << 7 | frame.opcode;
    frame_data[1] |= frame.mask << 7 | frame.payload_len;
    
    if(frame.payload_len == 126) {
        memcpy(frame_data+2, &length, sizeof(length));
    } else if(frame.payload_len == 127) {
        memcpy(frame_data+2, &length, sizeof(length));
    }
    
    memcpy(frame_data + (2 + (frame.payload_len > 125 ? (frame.payload_len == 126 ? 2 : 8) : 0)), data, length);
    
    // send the frame to client
    int sent = send(sockfd, frame_data, frame_size, 0);
    if(sent != frame_size) {
        cerr << "Error sending WebSocket frame" << endl;
    }
    
    delete[] frame_data;
}
int main() {
    int sockfd; // assume the socket has been created and connected to a client
    
    // ...
    
    const char* message = "Hello, World!";
    sendWebSocketData(sockfd, message, strlen(message), TEXT_FRAME);
    
    // ...
    
    return 0;
}

这个示例代码演示了如何使用 C++ 构建 WebSocket 数据帧并将其发送回客户端。函数 sendWebSocketData 接受套接字文件描述符、要发送的数据、数据长度和帧类型作为参数。该函数首先根据数据长度确定负载的长度，并构建 WebSocket 帧头部。然后将负载数据复制到 WebSocket 帧中并发送给客户端。

请注意，此示例代码仅演示了如何构建 WebSocket 数据帧。在实际应用中，您需要考虑更多的因素，例如数据的加密和解密、授权等。