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。
