一个简单的局域网多播示例

 
/*
*描述:一个简单的局域网多播示例(MultiCast In LAN. C++ Sample Codes)
*作者:魏孙鼎
*Email:weisunding@gmail.com
*2005年6月21日,广州
*/

#include <iostream>
#include <winsock2.h>
#include <ws2tcpip.h>

#pragma comment(lib, "ws2_32.lib") 

using namespace std; 

//---------------------------------------------------------------
#define MULTICAST_IP    "225.6.7.8" //多播组地址 224.0.0.0 - 239.255.255.255
#define MULTICAST_PORT  2100  //多播组端口 
#define BUFFER_SIZE     1024 
//---------------------------------------------------------------


void SendProc(void* arg); 
void RecvProc(void* arg);

//------------------------------------------------
//程序入口,为了程序简单清晰,省略SOCKET_ERROR的判断
//------------------------------------------------
int main() 
{ 
 //socket 初始化
 WSAData wsaData; 
 if( WSAStartup(MAKEWORD(2,0), &wsaData) != 0 ) {
  cout<<"Error in WSAStartup"<<endl; 
  return 0; 
 }

 SOCKET server; 
 server = socket(AF_INET, SOCK_DGRAM, 0); //创建一个UDP套接口 

 int ret;

 //允许程序的多个实例运行在同一台机器上 
 const int on = 1; 
 ret = setsockopt(server, SOL_SOCKET, SO_REUSEADDR, (char *)&on, sizeof(on)); 

 //设置TTL - Time To Live
 const int routenum = 10; 
 ret = setsockopt(server,IPPROTO_IP,IP_MULTICAST_TTL,(char*)&routenum,sizeof(routenum)); 

 //设置回馈,1表示可回馈到本机
 const int loopback = 1; 
 ret = setsockopt(server,IPPROTO_IP,IP_MULTICAST_LOOP,(char*)&loopback,sizeof(loopback)); 
  
 //设置本地地址，端口与多播端口一致
 sockaddr_in local;  
 local.sin_family = AF_INET; 
 local.sin_port   = htons(MULTICAST_PORT); 
 local.sin_addr.S_un.S_addr = INADDR_ANY; 

 //绑定到本地端口
 ret = bind(server, (sockaddr*)(&local), sizeof(local)); 
 
 //设置多播组结构
 ip_mreq mreq;  
 mreq.imr_interface.S_un.S_addr = INADDR_ANY;     //本地地址
 mreq.imr_multiaddr.S_un.S_addr = inet_addr(MULTICAST_IP); //多播地址

 //加入一个多播组
 ret = setsockopt(server,IPPROTO_IP,IP_ADD_MEMBERSHIP,(char*)&mreq,sizeof(mreq)); 


 //创建发送线程
 HANDLE hSend = CreateThread(NULL,
        NULL,
        (LPTHREAD_START_ROUTINE)SendProc,
        (void *)server,
        NULL,
        NULL);


 //创建读多播组数据线程
 HANDLE hRead = CreateThread(NULL,
        NULL,
        (LPTHREAD_START_ROUTINE)RecvProc,
        (void *)server,
        NULL,
        NULL);

 

 //如果用户输入结束，程序就终止了 
 WaitForSingleObject(hSend, INFINITE); 
 WSACleanup(); 

 return 0; 
} 


//-----------------------------------
//读取用户输入并发送到多播组线程函数 
//-----------------------------------
void SendProc(void* arg) 
{ 
 SOCKET server = (SOCKET)arg; 
 char sendline[BUFFER_SIZE+1]; 

 //设置多播地址
 sockaddr_in remote;  
 remote.sin_addr.s_addr = inet_addr ( MULTICAST_IP ); 
 remote.sin_family = AF_INET ; 
 remote.sin_port   = htons(MULTICAST_PORT); 

 cout<<"发送线程已启动,请输入(输入end结束)..."<<endl;

 //读取用户输入直到用户输入"end" 
 for(;;) 
 {   
  cin.getline(sendline, BUFFER_SIZE); 
  
  if(strncmp(sendline,"end",3)==0) 
   break; 

  //发送用户输入的数据到多播组 
  sendto(server, sendline, strlen(sendline), 0, (sockaddr*)(&remote), sizeof(remote)); 
 } 

 cout<<"发送线程结束..."<<endl;
} 


//----------------------------------
//读取多播组数据函数
//----------------------------------
void RecvProc(void* arg) 
{ 
 SOCKET server = (SOCKET)arg; 

 char buf[BUFFER_SIZE+1] = "/0"; 
 int ret; 

 sockaddr_in client; 
 int clientLen; 

 //一直读取直到主线程终止 
 for(;;)
 { 
  clientLen = sizeof(client); 
  memset(buf,0, sizeof(buf));

  ret = recvfrom(server, buf, BUFFER_SIZE, 0, (sockaddr*)(&clientLen), &clientLen); 
  
  if (ret == 0) 
   continue;

  if (ret > 0)
  {
   cout<<"=============================================="<<endl;
   cout<<"接收到"<<ret<<"字节:"<<endl;
   cout<<buf<<endl;
   cout<<"----------------------------------------------"<<endl;
  }
 } 

 cout<<"接收线程结束 ..."<<endl;