c - 加入多播组的所有端点都应该接收发送到该组的数据吗？

Question

如果两个端点连接起来在两个端口上表示 100 个多播组，现在如果我将数据发送到一个组地址和端口 Comb(g1,p1)，它是否也不会被其他套接字接收，因为它们也是该组的成员。

如果没有，为什么不呢？如果是，那么下面的代码有什么问题？

#include "stdafx.h"
#include <stdio.h>
#include <winsock2.h>

void socketCreation(void)
{
  unsigned int i=0;
  u_int    yes=1;

  for(i=0;i<gConfiguration.numSockets;i++)  //200
  {
    if ((gConfiguration.sockArray[i] = WSASocket(AF_INET,SOCK_DGRAM,IPPROTO_UDP,NULL,0,0))== INVALID_SOCKET)
    {
      printf("\n\t Socket Creation failed with error ::%d::", WSAGetLastError());
      WSACleanup();
      exit(1);
    }
    // Allow Multiple Sockets to use the same PORT number */
    if (setsockopt(gConfiguration.sockArray[i],SOL_SOCKET,SO_REUSEADDR,(char*)&yes,sizeof(yes)) < 0) 
    {
      printf("\n\t SetSockOpt for SO_REUSEADDR failed with error ::%d::", WSAGetLastError());
      WSACleanup();
      exit(1);
    }
  }

}

void socketBinding(void)
{
  struct     sockaddr_in addr;
  unsigned int i=0;
  unsigned int j=0;
  unsigned int tempPort =0;
  long localaddr  = inet_addr("127.0.0.1");
  int k = 0;
  for(i = 0;i<gConfiguration.numPorts;i++)
    {
      addr.sin_port=htons(gConfiguration.ports[i]);
      addr.sin_family=AF_INET;
      addr.sin_addr.s_addr=htonl(INADDR_ANY);
      // bind to receive address
      if (bind(gConfiguration.sockArray[i],(struct sockaddr *) &addr,sizeof(addr)) == SOCKET_ERROR) 
      {
        printf("\n\t Bind failed with error ::%d::", WSAGetLastError());
        exit(1);
      }
      printf("\n socket %d bind to port %d\t\n", gConfiguration.sockArray[i], gConfiguration.ports[i]);
      k++;
    }  
}
void joinMCastGroup(void)
{
  struct     ip_mreq mreq = {0};
  unsigned int i=0;
  unsigned int j=0;

  mreq.imr_interface.s_addr=htonl(INADDR_ANY);
  for(i=0;i<gConfiguration.numSockets;i++)
  {
    //In order to be a member of multiple MGroups run a loop
    for(j=0;j<gConfiguration.numAddress;j++)
    {
      //Select MulticastGroup
      mreq.imr_multiaddr.s_addr=gConfiguration.address[j];

      if (setsockopt(gConfiguration.sockArray[i],IPPROTO_IP,IP_ADD_MEMBERSHIP,(char*)&mreq,sizeof(mreq)) < 0) 
      {
        printf("\n\t Setsocketopt IP_ADD_MEMBERSHIP failed with::%d:: on ::%d:: socket",  WSAGetLastError(),j);
        exit(1);
      }
      //printf("\n %d socket is a member of the group add = %d,\n", i, gConfiguration.address[j]);
    }
  }
}

void dataRecv(void)
{
  int        retVal=-1;
  int        nBytes=-1;
  int        addrLen=0;
  char      buffer[MSG_BUF_SIZE];
  struct      sockaddr_in addr;
  fd_set      readFD;
  unsigned int  i=0;
  unsigned int    tickCount =0;

  gLastTickCount=GetTickCount();
  long lTotalPkt = 0;
  timeval timeout;
  timeout.tv_sec = 10;
  timeout.tv_usec = 100000;
  DWORD dwWaitResult = 0;
//  system("cls");
  printf("\n *********************************************** ");
  printf("\n Waiting for packets to come...");
  printf("\n ***********************************************\n ");
  addrLen=sizeof(addr);

  printf("\n Total Seq no to recv = %d\n", gTotalPkt);
  gSeqNo2 = 0;
  dwWaitResult = WaitForSingleObject(mutex, INFINITE);
  if(dwWaitResult == WAIT_OBJECT_0)
  {
    while(1)
    {
      FD_ZERO(&readFD);
      for(i=0;i<gConfiguration.numSockets;i++)
        FD_SET(gConfiguration.sockArray[i],&readFD);

      retVal=select(FD_SETSIZE,&readFD,NULL,NULL,&timeout);

      if(0<retVal)
      {
        for(i=0;i<gConfiguration.numSockets;i++)
        {
          if(FD_ISSET(gConfiguration.sockArray[i],&readFD))
          {
            addrLen=sizeof(addr);
            if ((nBytes=recvfrom(gConfiguration.sockArray[i],buffer,sizeof(buffer),0,(struct sockaddr *) &addr,&addrLen)) < 0) 
            {
              printf("\n\t RecvFrom Error with::%d::\n", WSAGetLastError());
              exit(1);
            }
            //printf("\n recvd on socket no = %d, data=%s, address = %d\n", i, buffer, gConfiguration.address[i]);
            gSeqNo2++;
            gBytesCount++;//= nBytes;
            gTotalByteReceived += gBytesCount;
          }
        }
        //tickCount = GetTickCount();
        //if((tickCount - gLastTickCount) > 1000) //Checking if it's more than 2 seconds or not
        //{

      }
      else
      {
        printf("timeout\n");
      }
      if(gTotalPkt == gSeqNo2)
      {
        printf("\n %d packets recvd.\n", gSeqNo2);
        ReleaseMutex(mutex);
        break;
      }

    }
  }
  ReleaseMutex(mutex);

  printf("\n Total packet Received= %d\n", gSeqNo2);
}
void RecvUsingThread()
{
  int i = 0;
  gtCount = 2;
  gTotalPkt =  gConfiguration.numPacket * gConfiguration.numAddress * gConfiguration.numPorts;//atol(buffer);
  mutex = CreateMutex(NULL, FALSE, NULL);
  if(NULL == mutex)
  {
    printf("\nunable to create mutex.\n.");
  }
  for(i = 0;i<gtCount;i++)
  {
    threadHandle[i] = CreateThread(NULL, 0, ( LPTHREAD_START_ROUTINE )dataRecv, NULL, 0, &threadId[i]);
    if (threadHandle[i] == NULL) 
       {
          printf("Unable to create Thread\n");
       }
  }
  WaitForMultipleObjects(gtCount, threadHandle, TRUE, INFINITE);
  for(i = 0;i<gtCount;i++)
  {
    CloseHandle(threadHandle[i]);
  }

  printf("\nTotal packet recvd = %d\n", gSeqNo2);
}

void socketOperations(void)
{
  int      retVal=-1;
  WSADATA    WsaData;
  // Initialize Winsock version 2.2
  if ((retVal = WSAStartup(MAKEWORD(2,2), &WsaData)) != 0)
  {
    // NOTE: Since Winsock failed to load we cannot use WSAGetLastError 
       // to determine the error code as is normally done when a Winsock 
       // API fails. We have to report the return status of the function.
    printf("\n\t WSAStartup failed with error ::%d::", retVal);
       exit(1);
  }

  //Creating Sockets and setting the SO_REUSEADDR option
  socketCreation();
  //Binding Sockets
  socketBinding();
  //Joining with the Multicast Group.
  joinMCastGroup();
  //Receiving the data on a Socket.
  RecvUsingThread();
}
//100AddrOn2Ports

Answer 1

端口是最终目的地，而不是多播组。

因此，发送到端口 100 的数据包 A 将通过其连接的任何组到达任何已连接的应用程序，除非平台是 Windows，因为 WinSock 提供比 Unix 额外的过滤主机。

您必须使用唯一的多播组和 UDP 端口对，仅将该对视为唯一的元组是不够的。

使用 226.0.0.1:500、226.0.0.2:502 等，不要使用226.0.0.1:500、226.0.0.2:500 等