[网络协议]简单的UDP网络程序

udpServer.cc

#include "udpServer.hpp"

void Usage(std::string proc)
{
    std::cout << "Usage: " << proc << " port" <<std::endl;
}

//./udpServer ip port
int main(int argc, char *argv[])
{
    if(argc != 2){//等于2是合法的
        Usage(argv[0]);
        exit(1);
    }
    udpServer *up = new udpServer(atoi(argv[1]));
    up->initServer();
    up->start();

    delete up;
}

udpServer.hpp

#pragma once 
#include<iostream>
#include<string>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netinet/in.h>
class udpServer 
{
  private:
    std::string ip;
    int port;
    int sock;
  public:
  //构造函数
    //udpServer(std::string _ip = "127.0.0.1",int _port=8080)
        //:ip(_ip),port(_port)
        udpServer(int _port=8080)
          ：port(_port)
    {}
    //初始化服务器
    void initServer()
    {//SOCK_STREAM是基于TCP的，数据传输比较有保障。SOCK_DGRAM是基于UDP的，专门用于局域网，基于广播SOCK_STREAM 是数据流,一般是tcp/ip协议的编程,SOCK_DGRAM分是数据抱,是udp协议网络编程
      sock = socket(AF_INET,SOCK_DGRAM,0);//1.创建套接字
      std:: cout <<"sock:"<< sock <<std:: endl;
      //2.填充结构体协议，ip，port
      struct sockaddr_in local;
      local.sin_family = AF_INET;
      local.sin_port = htons(port);
      local.sin_addr.s_addr = INADDR_ANY;
      //local.sin_addr.s_addr = inet_addr(ip.c_str());
      //网络地址为INADDR_ANY，这个宏表示本地的任意IP地址，因为服务器可能有多个网卡，每个网卡也可能绑定多个IP地址，这样设置可以在所有的IP地址上监听，直到与某个客户端建立了连接时才确定用哪个IP地址。
      
	//3.绑定端口，失败则直接结束进程
      if(bind(sock, (struct sockaddr*)& local,sizeof(local)) < 0)
      {
        std::cerr << "bind error!\n" << std::endl;
        exit(1);
      }
    }
    //echo server 
    //启动服务器
    void start()
    {
    //1.创建字符串接收数据
      char msg[64];
      for(;;){
      //定义远端addr结构体用于接收ip地址等
        msg[0] = '\0';
        struct sockaddr_in end_point;
        socklen_t len = sizeof(end_point);
        ssize_t s = recvfrom(sock,msg,sizeof(msg)-1,0,\
            (struct sockaddr*)&end_point,&len);//尝试读取请求
        if(s > 0){
          msg[s] = '\0';
          std::cout << "client#" << msg <<std:: endl;
          std::string echo_string = msg;
          echo_string += " [server echo]";
          //返回响应给客户端
          sendto (sock, echo_string.c_str(),echo_string.size(),\
              0,(struct sockaddr*)&end_point,len);
        }
      }
    }
    ~udpServer()
    {
      close(sock);
    }
};

udpClient.cc

#include "udpClient.hpp"

void Usage(std::string proc)
{
    std::cout <<"Usage: "<< proc << " svr_ip svr_port" << std::endl;
}

int main(int argc, char *argv[])
{
    if(argc != 3){
        Usage(argv[0]);
        exit(1);
    }
    udpClient uc(argv[1], atoi(argv[2]));
    uc.initClient();
    uc.start();

    return 0;
}

客户端不需要bind，但是需要IP和port

1. 在进行bind的时候，很容易冲突!客户端无法启动
2. 客户端需要唯一性，但是不需要明确必须是哪个端口号
3. 但是需要IP和port：client udp，recv 和send时，系统会自动进行ip和端口号绑定

udpClient.hpp

#pragma once 
#include<iostream>
#include<string>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netinet/in.h>
class udpClient 
{
  private:
    std::string ip;//ip地址
    int port;//端口号
    int sock;//套接字文件描述符
  public:
    //ip port? server ip,port
    //构造函数 
    udpClient(std::string _ip = "127.0.0.1",int _port=8080)
        :ip(_ip),port(_port)
    {}
    //初始化
    void initClient()
    {
    //创建套接字
      sock = socket(AF_INET,SOCK_DGRAM,0);
      std:: cout <<"sock:"<< sock <<std:: endl;
      //struct sockaddr_in local;
      //local.sin_family = AF_INET;
      //local.sin_port = htons(port);
      //local.sin_addr.s_addr = inet_addr(ip.c_str());

      //if(bind(sock, (struct sockaddr*)& local,sizeof(local)) < 0)
      //{
      //  std::cerr << "bind error!\n" << std::endl;
      //  exit(1);
      //}
    }
    //echo server 
    void start()
    {
      std::string msg;
      struct sockaddr_in peer;
      peer.sin_family = AF_INET;
      peer.sin_port = htons(port);
      peer.sin_addr.s_addr = inet_addr(ip.c_str());
   //   char msg[64];
      for(;;){
        std :: cout << "Please Enter# ";
        std :: cin >> msg;
        if(msg == "quit")
        {
          break;
        }
        //明确客户端发送报文时给谁发
        sendto(sock , msg.c_str(),msg.size(),0,(struct sockaddr*)& peer,sizeof(peer) );
        char echo[128];
        ssize_t s = recvfrom(sock,echo,sizeof(echo)-1, 0,nullptr,nullptr);
        if(s>0)
        {
          echo[s] = 0;
          std::cout << "server#" << echo << std::endl;
        }
    //    msg[0] = '\0';
    //    struct sockaddr_in end_point;
    //    socklen_t len = sizeof(end_point);
    //    ssize_t s = recvfrom(sock,msg,sizeof(msg)-1,0,\
    //        (struct sockaddr*)&end_point,&len);
    //    if(s > 0){
    //      msg[s] = '\0';
    //      std::cout << "client#" << msg <<std:: endl;
    //      std::string echo_string = msg;
    //      echo_string += " [server echo]";
    //      sendto (sock, echo_string.c_str(),echo_string.size(),\
    //          0,(struct sockaddr*)&end_point,len);
    //    }
      }
    }
    ~udpClient()
    {
      close(sock);
    }
};