（3）同步读写client和server

今天我们来实现一个最基础的 TCP 通信。
客户端：从终端读取一行输入，发送给服务端，再接收服务端回传的数据

服务端：监听指定端口，接收客户端连接，为每个连接创建一个线程，读取客户端消息并原样返回

一、整体通信流程

客户端流程

1. 创建 io_context
2. 构造服务端地址和端口对应的 endpoint
3. 创建 socket
4. 调用 connect() 连接服务端
5. 从控制台读入用户输入
6. 调用 write() 发送数据
7. 调用 read() 接收服务端回传数据

服务端流程

1. 创建 io_context
2. 创建 acceptor 并绑定到 10086 端口
3. 循环等待客户端连接
4. 每接收一个客户端，就创建一个 socket
5. 为该连接启动一个线程执行 session()
6. 在线程中循环读取客户端数据
7. 收到数据后原样写回，实现 Echo

二、客户端代码

#include<boost/asio.hpp>#include<iostream>usingnamespaceboost;constintMAX_LENGTH=1024;intmain(){try{//创建上下文服务asio::io_context ioc;//构造一个endpointasio::ip::tcp::endpointremote_ep(asio::ip::make_address("127.0.0.1"),10086);asio::ip::tcp::socketsock(ioc);system::error_code error=asio::error::host_not_found;sock.connect(remote_ep,error);if(error){std::cout<<"connect failed code is "<<error.value()<<"error msg is"<<error.message()<<std::endl;return0;}std::cout<<"Enter Message: ";charrequest[MAX_LENGTH];std::cin.getline(request,MAX_LENGTH);size_t request_length=strlen(request);asio::write(sock,asio::buffer(request,request_length));charreply[MAX_LENGTH];size_t reply_length=asio::read(sock,asio::buffer(reply,request_length));std::cout<<"Reply is : ";std::cout.write(reply,reply_length);std::cout<<"\n";}catch(system::system_error&e){std::cerr<<"Exception"<<e.what()<<std::endl;}}

三、服务端代码

#include<boost/asio.hpp>#include<iostream>#include<memory>#include<set>usingnamespaceboost;constintMAX_LENGTH=1024;usingsocket_ptr=std::shared_ptr<asio::ip::tcp::socket>;std::set<std::shared_ptr<std::thread>>thread_set;voidsession(socket_ptr sock){try{for(;;){chardata[MAX_LENGTH];memset(data,'\0',MAX_LENGTH);system::error_code error;//size_t length = asio::read(sock, asio::buffer(data, MAX_LENGTH), error);size_t length=sock->read_some(asio::buffer(data,MAX_LENGTH),error);if(error==asio::error::eof){std::cout<<"connection closed by peer"<<std::endl;break;}elseif(error){throwsystem::system_error(error);}std::cout<<"receive form "<<sock->remote_endpoint().address().to_string()<<std::endl;std::cout<<"receive message is "<<data<<std::endl;//回传给对方asio::write(*sock,asio::buffer(data,MAX_LENGTH));}}catch(system::system_error&e){std::cerr<<"error in thread: "<<e.what()<<"\n"<<std::endl;}return;}voidserver(asio::io_context&io_context,uint16_tport){asio::ip::tcp::acceptora(io_context,asio::ip::tcp::endpoint(asio::ip::tcp::v4(),port));for(;;){socket_ptrsocket(newasio::ip::tcp::socket(io_context));a.accept(*socket);autot=std::make_shared<std::thread>(session,socket);thread_set.insert(t);}}intmain(){try{asio::io_context ioc;server(ioc,10086);for(auto&t:thread_set){t->join();}}catch(system::system_error&e){std::cerr<<"error in thread: "<<e.what()<<"\n"<<std::endl;}return0;}