Webrtc 信令服务器实现

webrtc建联流程图

由上图可知，所谓的信令服务器其实就是将peer的offer/candidate/answer传给对端而已。这样的话实现方式就有很多种了，目前普遍的方式HTTP/HTTPS，WS/WSS。像webrtc-demo-peerconnection就是实现HTTP这种方式。本文使用WS（websocket）来实现。

简单的协议

peer签到

发送

src	type
就是peer的名称	signin

type	code	msg
signin_ack	返回码	消息

peer数据传输

发送

src	dst	type	其他内容
发送端名称	接收端名称	trans	...

type	code	msg
trans_ack	返回码	消息

实现代码

1、下载websocketpp/jsoncpp代码：github上找

2、下载boost库

3、先使用cmake生成VS工程，然后编译jsoncpp

4、创建工程SignalServer

主代码如下：

#include "pch.h"
#include <iostream>
#include <websocketpp/config/asio_no_tls.hpp>
#include <websocketpp/server.hpp>
#include <json/json.h>
typedef websocketpp::server<websocketpp::config::asio> server;
server signalserver;
std::mutex g_wcmutex;
std::map<std::string, websocketpp::connection_hdl> g_mapWcInfo;
void on_message(websocketpp::connection_hdl hdl, server::message_ptr msg)
{
   std::string strMsg = msg->get_payload();
   //解析json
   Json::Reader reader;
   Json::Value jMsg;
   if (!reader.parse(strMsg, jMsg))
   {
       return;
   }
   //获取当前的用户名称
   std::string strSrcName;
   Json::Value jName;
   if (!jMsg.isMember("src"))
   {
       return;
   }

   jName = jMsg["src"];
   strSrcName = jName.asString();
   //获取当前的操作
   std::string strOptType;
   Json::Value jOptType;
   if (!jMsg.isMember("type"))
   {
       return;
   }

   jOptType = jMsg["type"];
   strOptType = jOptType.asString();
   //数据转发
   if (strOptType.compare("signin") == 0)//peer签到
   {
       try {
           g_wcmutex.lock();
           g_mapWcInfo[strSrcName] = hdl;
           g_wcmutex.unlock();
           signalserver.send(hdl, "{\"type_ack\":\"signin\",\"code\":200,\"msg\":\"success\"}", websocketpp::frame::opcode::text);
       }
       catch (websocketpp::exception const & e) {
           std::cout << "Echo failed because: "
               << "(" << e.what() << ")" << std::endl;
       }
   }
   else if (strOptType.compare("trans") == 0)//数据转发
   {
       std::string strDstName;
       Json::Value jDstName;
       if (!jMsg.isMember("dst"))
       {
           return;
       }
       jDstName = jMsg["dst"];
       strDstName = jDstName.asString();
       g_wcmutex.lock();
       if (g_mapWcInfo.find(strDstName) == g_mapWcInfo.end())
       {
           g_wcmutex.unlock();
           signalserver.send(hdl, "{\"trans_ack\":\"trans\",\"code\":201,\"msg\":\"failed\"}", websocketpp::frame::opcode::text);
           return;
       }
       else
       {
           signalserver.send(g_mapWcInfo[strDstName], strMsg, websocketpp::frame::opcode::text);
           signalserver.send(hdl, "{\"trans_ack\":\"trans\",\"code\":200,\"msg\":\"success\"}", websocketpp::frame::opcode::text);
       }
       g_wcmutex.unlock();

   }
}

void on_close(websocketpp::connection_hdl hdl)
{
   server::connection_ptr ptr = signalserver.get_con_from_hdl(hdl);
   g_wcmutex.lock();
   std::map<std::string, websocketpp::connection_hdl>::iterator it = g_mapWcInfo.begin();
   while (it != g_mapWcInfo.end())
   {
       server::connection_ptr ptr1 = signalserver.get_con_from_hdl(it->second);
       if (ptr1 == ptr)
       {
           g_mapWcInfo.erase(it);
           break;
       }
   }
   g_wcmutex.unlock();
}

int main()
{
   signalserver.set_close_handler(&on_close);
   signalserver.set_message_handler(&on_message);
   signalserver.set_access_channels(websocketpp::log::alevel::all);
   signalserver.set_error_channels(websocketpp::log::elevel::all);
   signalserver.init_asio();
   signalserver.listen(9002);
   signalserver.start_accept();
   signalserver.run();
}