c++服务器websocket支持

迷南。 2022-05-08 15:48 270阅读 0赞

From: [https://blog.csdn.net/u010223072/article/details/80637127][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。

[https_blog.csdn.net_u010223072_article_details_80637127]: https://blog.csdn.net/u010223072/article/details/80637127