From: https://blog.csdn.net/u010223072/article/details/80637127
介绍
目前公司服务器是c++ tcp的网络架构，现在想用这套做h5游戏，所以要扩展支持websocket通信。
那么什么是websocket？它和tcp有什么区别？这些随便一搜一大把，这里就不再科普达。通俗简单点讲websocket就是山寨版的tcp，它底层实现就是tcp，唯一的区别就是网络传输时websocket协议前面多了个标志它的包头信息。去掉前面这部分包头剩下的就和普通tcp一样了。
那么讲到这里，在现有tcp上怎么扩展支持websocket？其实就很简单呢！既然它和tcp协议上就只是多了个包头部分，那么我们的任务其实主要就是怎么解析这个包头信息了。
最后，还有一个需要注意的细节是websocket协议前后端建立连接前需要一次握手协议，触发时机是client发起connet连接请求时，会向server发送这条握手的协议，server收到后要回复client，这样就建立了连接了。
好～闲话少说，下面直接上实现代码…
实现
1.握手。
client第一次connet连接会发起握手协议，server在recv接收处解析，判断如果是websocket的握手协议，那么同样组装好特定格式包头回复给client，建立连接。
判断是不是websocket协议
bool isWSHandShake(std::string &request)
{
size_t i = request.find("GET");
if(i == std::string::npos){
return false;
}
return true;
}
如果是，解析握手协议重新组装准备send回复给client
bool wsHandshake(std::string &request, std::string &response)
{
//得到客户端请求信息的key
std::string tempKey = request;
size_t i = tempKey.find("Sec-WebSocket-Key");
if(i == std::string::npos){
return false;
}
tempKey = tempKey.substr(i + 19, 24);
//拼接协议返回给客户端
response = "HTTP/1.1 101 Switching Protocols\r\n";
response += "Connection: upgrade\r\n";
response += "Sec-WebSocket-Accept: ";
std::string realKey = tempKey;
realKey += "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
SHA1 sha;
unsigned int message_digest[5];
sha.Reset();
sha << realKey.c_str();
sha.Result(message_digest);
for (int i = 0; i < 5; i++) {
message_digest[i] = htonl(message_digest[i]);
}
realKey = base64_encode(reinterpret_cast<const unsigned char*>(message_digest), 20);
realKey += "\r\n";
response += realKey.c_str();
response += "Upgrade: websocket\r\n\r\n";
return true;
}
2.接收client协议解析
首先解析包头信息
bool wsReadHeader(const unsigned char* cData, WebSocketStreamHeader* header)
{
if (cData == NULL) return false;
const unsigned char *buf = cData;
header->fin = buf[0] & 0x80;
header->masked = buf[1] & 0x80;
unsigned char stream_size = buf[1] & 0x7F;
header->opcode = buf[0] & 0x0F;
if (header->opcode == WS_FrameType::WS_CONTINUATION_FRAME) {
//连续帧
return false;
}
else if (header->opcode == WS_FrameType::WS_TEXT_FRAME) {
//文本帧
}
else if (header->opcode == WS_FrameType::WS_BINARY_FRAME) {
//二进制帧
}
else if (header->opcode == WS_FrameType::WS_CLOSING_FRAME) {
//连接关闭消息
return true;
}
else if (header->opcode == WS_FrameType::WS_PING_FRAME) {
// ping
return false;
}
else if (header->opcode == WS_FrameType::WS_PONG_FRAME) {
// pong
return false;
}
else {
//非法帧
return false;
}
if (stream_size <= 125) {
// small stream
header->header_size =6;
header->payload_size = stream_size;
header->mask_offset = 2;
}
else if (stream_size == 126) {
// medium stream
header->header_size = 8;
unsigned short s = 0;
memcpy(&s, (const char*)&buf[2], 2);
header->payload_size = ntohs(s);
header->mask_offset = 4;
}
else if (stream_size == 127) {
unsigned long long l = 0;
memcpy(&l, (const char*)&buf[2], 8);
header->payload_size = l;
header->mask_offset = 10;
}
else {
//Couldnt decode stream size 非法大小数据包
return false;
}
/* if (header->payload_size > MAX_WEBSOCKET_BUFFER) {
return false;
} */
return true;
}
然后根据包头解析出真是数据
bool wsDecodeFrame(const WebSocketStreamHeader& header, unsigned char cbSrcData[], unsigned short wSrcLen, unsigned char cbTagData[])
{
const unsigned char *final_buf = cbSrcData;
if (wSrcLen < header.header_size + 1) {
return false;
}
char masks[4];
memcpy(masks, final_buf + header.mask_offset, 4);
memcpy(cbTagData, final_buf + header.mask_offset + 4, header.payload_size);
for (INT_PTR i = 0; i < header.payload_size; ++i){
cbTagData[i] = (cbTagData[i] ^ masks[i % 4]);
}
//如果是文本包，在数据最后加一个结束字符“\0”
if (header.opcode == WS_FrameType::WS_TEXT_FRAME)
cbTagData[header.payload_size] = '\0';
return true;
}
3.组装server发给client协议
bool wsEncodeFrame(std::string inMessage, std::string &outFrame, enum WS_FrameType frameType)
{
const uint32_t messageLength = inMessage.size();
if (messageLength > 32767)
{
// 暂不支持这么长的数据
return false;
}
uint8_t payloadFieldExtraBytes = (messageLength <= 0x7d) ? 0 : 2;
// header: 2字节, mask位设置为0(不加密), 则后面的masking key无须填写, 省略4字节
uint8_t frameHeaderSize = 2 + payloadFieldExtraBytes;
uint8_t *frameHeader = new uint8_t[frameHeaderSize];
memset(frameHeader, 0, frameHeaderSize);
// fin位为1, 扩展位为0, 操作位为frameType
frameHeader[0] = static_cast<uint8_t>(0x80 | frameType);
// 填充数据长度
if (messageLength <= 0x7d)
{
frameHeader[1] = static_cast<uint8_t>(messageLength);
}
else
{
frameHeader[1] = 0x7e;
uint16_t len = htons(messageLength);
memcpy(&frameHeader[2], &len, payloadFieldExtraBytes);
}
// 填充数据
uint32_t frameSize = frameHeaderSize + messageLength;
char *frame = new char[frameSize + 1];
memcpy(frame, frameHeader, frameHeaderSize);
memcpy(frame + frameHeaderSize, inMessage.c_str(), messageLength);
outFrame = std::string(frame, frameSize);
delete[] frame;
delete[] frameHeader;
return true;
}
至此，tcp上扩展websocket所需要处理的3大块就都完成了，即握手、接收解析、发送组装。