多播报文的发送和接收

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1      实验目的

掌握多播的原理及如何进行多播报文的发送和接受

2      注意事项

需包括ws2tcpip.h文件

发送者和所有接受者在同一网内

不考虑TTL值,回环状态

通过setsockopt( )函数设置选项来实现多播数据的发送和接收

3      试验流程

3.1  多播数据发送端流程

l  创建一个数据报套接口

l  设置多播地址(例:239.192.1.2)和端口号(例:12345)

l  调用setsockopt( )函数设置发送的数据报本地接口(IP_MULTICAST_IF)

struct in_addr interface_addr;

setsockopt ( socket, IPPROTO_IP, IP_MULTICAST_IF,

                    &interface_addr,sizeof(interface_addr) );

l  使用sendto函数发送数据,目标地址为第二步所设置的多播地址

3.2  多播数据接收的流程

l  创建数据报套接口

l  绑定本地地址(INADDR_ANY)和端口号(同发送端)

l  调用setsockopt( )函数设置IP_ADD_MEMBERSHIP选项,加入多播组

                 struct ip_mreq {

             struct in_addr imr_multiaddr;   /* IP multicast address of group */

             struct in_addr imr_interface;    /* local IP address of interface */

               };

                struct ip_mreq mreq;

                setsockopt ( socket, IPPROTO_IP,IP_ADD_MEMBERSHIP,

                       &mreq, sizeof(mreq));

l  接收数据

 

4      源代码

4.1  公共代码

#ifndef _MCASTLIB_H_

#define _MCASTLIB_H_

#include <Winsock2.h>

#include <WS2tcpip.h>

 

#ifdef __cplusplus

extern "C" {

#endif

int mc_join(SOCKET s,in_addr *mcaddr, in_addr *local_if);

int mc_setIF(SOCKET s,const DWORD local_out_if);

int mc_getIF(SOCKET s,DWORD *local_out_if);

int mc_setTTL(SOCKET s,const DWORD ttl);

int mc_getTTL(SOCKET s,DWORD *ttl);

int mc_setLoop(SOCKET s,const BOOL flag);

int mc_getLoop(SOCKET s,BOOL *flag);

int mc_leave(SOCKET s,in_addr *mcaddr, in_addr *local_if);

#ifdef __cplusplus

}

#endif

 

#endif // _MCASTLIB_H_

 

#include "MCastlib.h"

 

int mc_join(SOCKET s,in_addr *mcaddr, in_addr *local_if)

{

         ip_mreq mreq;

         memcpy(&(mreq.imr_interface), local_if,sizeof(in_addr)); // local if

         memcpy(&(mreq.imr_multiaddr), mcaddr, sizeof(in_addr));// multicast group address

         return (setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP,(char*)&mreq, sizeof(mreq)));

}

 

//为多播报文设置外出接口

int mc_setIF(SOCKET s,const DWORD local_out_if)

{

         return (setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF,(char*)&local_out_if, sizeof(local_out_if)));

}

 

// 获取多播报文的外出接口

int mc_getIF(SOCKET s, DWORD *local_out_if)

{

         intlen = sizeof(DWORD);

         return(getsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, (char*)&local_out_if,&len));

}

 

// 设置外出多播报文的TTL值,默认为1

int mc_setTTL(SOCKET s, const DWORD ttl)

{

         return(setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, (char*)&ttl, sizeof(ttl)));

}

 

// 获取外出多播报文的ttl

int mc_getTTL(SOCKET s, DWORD *ttl)

{

         intlen = sizeof(DWORD);

         return(getsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, (char*)ttl, &len));

}

 

// 启用或者禁止多播报文环回

int mc_setLoop(SOCKET s, const BOOL flag)

{

         return(setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, (char*)&flag, sizeof(flag)));

}

 

// 获取本地多播回环状态

int mc_getLoop(SOCKET s, BOOL *flag)

{

         intlen = sizeof(BOOL);

         return(getsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, (char*)flag, &len));

}

 

// 本地接口local_if离开多播组

int mc_leave(SOCKET s, in_addr *mcaddr,in_addr *local_if)

{

         ip_mreqmreq;

         memcpy(&(mreq.imr_interface),local_if, sizeof(in_addr)); // local if

         memcpy(&(mreq.imr_multiaddr),local_if, sizeof(in_addr)); // multicast group address

        

         return(setsockopt(s, IPPROTO_IP, IP_DROP_MEMBERSHIP, (char*)&mreq,sizeof(mreq)));

}

 

4.2  发送方

// 发送方

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

#include <stdio.h>

#include <WINSOCK2.H>

#include "MCastlib.h"

 

void HandleError(char *func);

int main()

{

         WSADatawsaData;

         WSAStartup(WINSOCK_VERSION,&wsaData);

 

         /*********创建一个数据报套接口****************/

         sockaddr_inlocal;

         memset(&local,0, sizeof(local));

         local.sin_addr.s_addr= htonl(INADDR_ANY);

         local.sin_family= AF_INET;

         local.sin_port= htons(12345);

         SOCKET sock = socket(AF_INET, SOCK_DGRAM, 0);

         /*********************************************/

 

         /****调用setsockopt( )函数设置发送的数据报本地接口(IP_MULTICAST_IF)****/

         if(mc_setIF(sock, sizeof(sock)) == SOCKET_ERROR)

         {

                   printf("mc_setIF:%d/n", WSAGetLastError());

         }

         /**********************************************************************/

/*     //获取默认的多播报文TTL值和回环状态

         DWORDttl;

         if(mc_getTTL(sock, &ttl) == SOCKET_ERROR)

         {

                   printf("mc_getTTL:%d/n", WSAGetLastError());

         }

        

         BOOLloop;

         if(mc_getLoop(sock, &loop) == SOCKET_ERROR)

         {

                   printf("mc_getLoop:%d/n", WSAGetLastError());

         }

         printf("Multicastdefault: TTL=%d,LoopBack=%d/n", ttl, loop);

 

         //设置TTL值为219

         ttl= 219;

         if(mc_setTTL(sock, ttl) == SOCKET_ERROR)

         {

                   printf("mc_setTTL:%d/n", WSAGetLastError());

         }

*/    

 

         /***************设置多播地址和端口号*************/

         sockaddr_in to;

         memset(&to, 0, sizeof(to));

         to.sin_addr.s_addr = inet_addr("239.192.1.2");

         to.sin_family = AF_INET;

         to.sin_port = htons(12345);

         /************************************************/

        

         /***使用sendto函数发送数据,目标地址为第二步所设置的多播地址****/

         charbuf[60];

         while(true)

         {

                   printf("INPUT:/n");

                   gets(buf);

                   buf[strlen(buf)]= '/0';

                   int res = sendto(sock, buf, strlen(buf) + 1, 0,(sockaddr*)&to, sizeof(to));

                   if(res == SOCKET_ERROR)

                   {

                            HandleError("sendto");

                   }

                   else

                   {

                            printf("Sendout %d bytes!/n", res);

                            if(strcmp(buf, "QUIT") == 0)

                            {

                                     break;

                            }

                   }

         }

         /***************************************************************/

         return0;

}

 

void HandleError(char *func)

{

         interrCode = WSAGetLastError();

         charinfo[65] = {0};

         _snprintf(info,64, "%s: %d/n", func, errCode);

         printf(info);

}

 

4.3  接收方

// 接收方

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

#include <stdio.h>

#include "MCastlib.h"

 

int main()

{

         //Init the winsock environment

         WSADatawsaData;

         if(WSAStartup(WINSOCK_VERSION, &wsaData) != 0)

         {

                   printf("Failedto Load a winsock./n");

                   return0;

         }

        

         //创建数据报套接口

         SOCKET sock = socket(AF_INET, SOCK_DGRAM, 0);

         if(sock == INVALID_SOCKET)

         {

                   printf("socket:%d/n", WSAGetLastError());

                   return0;

         }

         //绑定本地地址(INADDR_ANY)和端口号(同发送端)

         sockaddr_inlocal;

         memset(&local,0, sizeof(local));

         local.sin_family= AF_INET;

         local.sin_addr.s_addr= htonl(INADDR_ANY);

         local.sin_port= htons(12345);

 

         //bind local socket

         if (bind(sock, (sockaddr*)&local, sizeof(local)) ==SOCKET_ERROR)

         {

                   printf("bind:%d/n", WSAGetLastError());

                   return0;

         }

        

         //多播组地址

         in_addrmcaddr;

         mcaddr.S_un.S_addr = inet_addr("239.192.1.2");

         //加入多播组

         if (mc_join(sock, &mcaddr, &(local.sin_addr)) ==SOCKET_ERROR)

         {

                   printf("JoinMulticast Group: %d/n", WSAGetLastError());

         }

        

         //接收数据,考虑此时能收到发往哪些目的地址的UDP报文

         charbuf[65];

         while(true)

         {

                   memset(buf,0, 65);

                   if (recvfrom(sock, buf, 64, 0, NULL, NULL) ==SOCKET_ERROR)

                   {

                            printf("recvfrom:%d/n", WSAGetLastError());

                            break;

                   }

                   else

                   {

                            printf("recvd:%s/n", buf);

                            if(strcmp(buf, "QUIT") == 0)

                            {

                                     break;

                            }

                   }

         }

         return0;

}

 

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