由于需要在项目中增加Websocket协议，与客户端进行通信，不想使用开源的库，比如WebSocketPP，就自己根据WebSocket协议实现一套函数，完全使用C++实现。
代码已经实现，放在个人github上面，地址：https://github.com/jice1001/websocket.git。下面进行解释说明：
一、原理
Websocket协议解析，已经在前面博客里面详细讲解过，可以参考博客http://www.cnblogs.com/jice1990/p/5435419.html，这里就不详细细说。
服务器端实现就是使用TCP协议，使用传统的socket流程进行绑定监听，使用epoll控制多路并发，收到Websocket握手包时候进行握手处理，握手成功便可进行数据收发。
二、实现
1、服务器监听
该部分使用的是TCP socket流程，首先是通过socket函数建立socket,通过bind函数绑定到某个端口，本例使用的是9000，然后通过listen函数开启监听，代码如下：
listenfd_ = socket(AF_INET, SOCK_STREAM, 0);
if(listenfd_ == -1){
DEBUG_LOG("创建套接字失败!");
return -1;
}
struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(sockaddr_in));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
server_addr.sin_port = htons(PORT);
if(-1 == bind(listenfd_, (struct sockaddr *)(&server_addr), sizeof(server_addr))){
DEBUG_LOG("绑定套接字失败!");
return -1;
}
if(-1 == listen(listenfd_, 5)){
DEBUG_LOG("监听失败!");
return -1;
}
2、epoll控制多路并发
该部分使用的是epoll流程，首先在初始化时候使用epoll_create创建epoll句柄
```
epollfd_ = epoll_create(1024);
```
然后通过epoll_wait等待fd事件来临，当监听到是listenfd事件时候，说明是客户端连接服务器，就使用accept接受连接，然后注册该连接EPOLLIN事件，当epoll监听到EPOLLIN事件时候，即可进行握手和数据读取。代码如下：
void ctl_event(int fd, bool flag){
struct epoll_event ev;
ev.data.fd = fd;
ev.events = flag ? EPOLLIN : 0;
epoll_ctl(epollfd_, flag ? EPOLL_CTL_ADD : EPOLL_CTL_DEL, fd, &ev);
if(flag){
set_noblock(fd);
websocket_handler_map_[fd] = new Websocket_Handler(fd);
if(fd != listenfd_)
DEBUG_LOG("fd: %d 加入epoll循环", fd);
}
else{
close(fd);
delete websocket_handler_map_[fd];
websocket_handler_map_.erase(fd);
DEBUG_LOG("fd: %d 退出epoll循环", fd);
}
}
getbuff(), BUFFLEN)) <= 0){ ctl_event(fd, false); } else{ handler->process(); } } } } return 0; }" data-snippet-id="ext.51666c03e08fce92251ecc7459770145" data-snippet-saved="false" data-codota-status="done">int epoll_loop(){
struct sockaddr_in client_addr;
socklen_t clilen;
int nfds = 0;
int fd = 0;
int bufflen = 0;
struct epoll_event events[MAXEVENTSSIZE];
while(true){
nfds = epoll_wait(epollfd_, events, MAXEVENTSSIZE, TIMEWAIT);
for(int i = 0; i < nfds; i++){
if(events[i].data.fd == listenfd_){
fd = accept(listenfd_, (struct sockaddr *)&client_addr, &clilen);
ctl_event(fd, true);
}
else if(events[i].events & EPOLLIN){
if((fd = events[i].data.fd) < 0)
continue;
Websocket_Handler *handler = websocket_handler_map_[fd];
if(handler == NULL)
continue;
if((bufflen = read(fd, handler->getbuff(), BUFFLEN)) <= 0){
ctl_event(fd, false);
}
else{
handler->process();
}
}
}
}
return 0;
}
3、Websocket握手连接
握手部分主要是根据Websocket握手包进行解析，然后根据Sec-WebSocket-Key进行SHA1哈希，生成相应的key,返回给客户端，与客户端进行握手。代码如下：
//该函数是获取websocket握手包的信息，按照分割字符进行解析
int fetch_http_info(){
std::istringstream s(buff_);
std::string request;
std::getline(s, request);
if (request[request.size()-1] == '\r') {
request.erase(request.end()-1);
} else {
return -1;
}
std::string header;
std::string::size_type end;
while (std::getline(s, header) && header != "\r") {
if (header[header.size()-1] != '\r') {
continue; //end
} else {
header.erase(header.end()-1); //remove last char
}
end = header.find(": ",0);
if (end != std::string::npos) {
std::string key = header.substr(0,end);
std::string value = header.substr(end+2);
header_map_[key] = value;
}
}
return 0;
}
(message_digest),20); server_key += "\r\n"; strcat(request, server_key.c_str()); strcat(request, "Upgrade: websocket\r\n\r\n"); }" data-snippet-id="ext.1037e694d2a1acebfc3bc18153a74218" data-snippet-saved="false" data-codota-status="done">//该函数是根据websocket返回包的格式拼接相应的返回包
void parse_str(char *request){
strcat(request, "HTTP/1.1 101 Switching Protocols\r\n");
strcat(request, "Connection: upgrade\r\n");
strcat(request, "Sec-WebSocket-Accept: ");
std::string server_key = header_map_["Sec-WebSocket-Key"];
server_key += MAGIC_KEY;
SHA1 sha;
unsigned int message_digest[5];
sha.Reset();
sha << server_key.c_str();
sha.Result(message_digest);
for (int i = 0; i < 5; i++) {
message_digest[i] = htonl(message_digest[i]);
}
server_key = base64_encode(reinterpret_cast<const unsigned char*>(message_digest),20);
server_key += "\r\n";
strcat(request, server_key.c_str());
strcat(request, "Upgrade: websocket\r\n\r\n");
}
4、数据读取
当服务器与客户端握手成功后，就可以进行正常的通信，读取数据了。使用的是TCP协议的方法，解析Websocket包根据协议格式，在前面博客里面有详细分析，这里只把实现代码贴出来。
> 7; return 0; } int fetch_opcode(char *msg, int &pos){ opcode_ = msg[pos] & 0x0f; pos++; return 0; } int fetch_mask(char *msg, int &pos){ mask_ = (unsigned char)msg[pos] >> 7; return 0; } int fetch_masking_key(char *msg, int &pos){ if(mask_ != 1) return 0; for(int i = 0; i < 4; i++) masking_key_[i] = msg[pos + i]; pos += 4; return 0; } int fetch_payload_length(char *msg, int &pos){ payload_length_ = msg[pos] & 0x7f; pos++; if(payload_length_ == 126){ uint16_t length = 0; memcpy(&length, msg + pos, 2); pos += 2; payload_length_ = ntohs(length); } else if(payload_length_ == 127){ uint32_t length = 0; memcpy(&length, msg + pos, 4); pos += 4; payload_length_ = ntohl(length); } return 0; } int fetch_payload(char *msg, int &pos){ memset(payload_, 0, sizeof(payload_)); if(mask_ != 1){ memcpy(payload_, msg + pos, payload_length_); } else { for(uint i = 0; i < payload_length_; i++){ int j = i % 4; payload_[i] = msg[pos + i] ^ masking_key_[j]; } } pos += payload_length_; return 0; }" data-snippet-id="ext.87c0edbc59391ba5235ce52f85303829" data-snippet-saved="false" data-codota-status="done">int fetch_websocket_info(char *msg){
int pos = 0;
fetch_fin(msg, pos);
fetch_opcode(msg, pos);
fetch_mask(msg, pos);
fetch_payload_length(msg, pos);
fetch_masking_key(msg, pos);
return fetch_payload(msg, pos);
}
int fetch_fin(char *msg, int &pos){
fin_ = (unsigned char)msg[pos] >> 7;
return 0;
}
int fetch_opcode(char *msg, int &pos){
opcode_ = msg[pos] & 0x0f;
pos++;
return 0;
}
int fetch_mask(char *msg, int &pos){
mask_ = (unsigned char)msg[pos] >> 7;
return 0;
}
int fetch_masking_key(char *msg, int &pos){
if(mask_ != 1)
return 0;
for(int i = 0; i < 4; i++)
masking_key_[i] = msg[pos + i];
pos += 4;
return 0;
}
int fetch_payload_length(char *msg, int &pos){
payload_length_ = msg[pos] & 0x7f;
pos++;
if(payload_length_ == 126){
uint16_t length = 0;
memcpy(&length, msg + pos, 2);
pos += 2;
payload_length_ = ntohs(length);
}
else if(payload_length_ == 127){
uint32_t length = 0;
memcpy(&length, msg + pos, 4);
pos += 4;
payload_length_ = ntohl(length);
}
return 0;
}
int fetch_payload(char *msg, int &pos){
memset(payload_, 0, sizeof(payload_));
if(mask_ != 1){
memcpy(payload_, msg + pos, payload_length_);
}
else {
for(uint i = 0; i < payload_length_; i++){
int j = i % 4;
payload_[i] = msg[pos + i] ^ masking_key_[j];
}
}
pos += payload_length_;
return 0;
}
5、总结
到此为止，完整实现了使用C++对Websocket协议进行解析，握手，数据收发，不借助开源库就实现了websocket相关功能，最大程度的与项目保存兼容。
转自：http://www.cnblogs.com/jice1990/p/5436532.html
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