Linux&Windows下的IP Multicast 开发

 Multicast 不用多说，组播，既然要做multicast开发，肯定得知道multicast是什么；
windows和linux下开发的multicast的代码如下，具体的讲解，看代码注释：

C/C++ code

/*Multicast Client.c support Linux & Windows
*Zhao.kaiyong(a)gmail.com
*http://blog.csdn.net/openhero
*可以转载，可以复制，修改，如果有修改，请给我来一封email：）谢谢
*/

    
    
    
    

     
     
     
     
     
#include 
     
     
     
     <
     
     
     
     stdio.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     stdlib.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     string
     
     
     
     .h
     
     
     
     >
     
     
     
     

#ifdef _WIN32
#include 
     
     
     
     <
     
     
     
     winsock2.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     io.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     Ws2tcpip.h
     
     
     
     >
     
     
     
     


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


     
     
     
     #else
     
     
     
     
#include 
     
     
     
     <
     
     
     
     sys
     
     
     
     /
     
     
     
     types.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     sys
     
     
     
     /
     
     
     
     socket.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     netinet
     
     
     
     /
     
     
     
     in
     
     
     
     .h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     arpa
     
     
     
     /
     
     
     
     inet.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     unistd.h
     
     
     
     >
     
     
     
     
#include 
     
     
     
     <
     
     
     
     errno.h
     
     
     
     >
     
     
     
     

     
     
     
     #define
     
     
     
      closesocket close
     
     
     
     

     
     
     
     #endif
     
     
     
     


     
     
     
     #define
     
     
     
      BUF_SIZE 0x1000
     
     
     
     


     
     
     
     char
     
     
     
      
     
     
     
     *
     
     
     
      host_name 
     
     
     
     =
     
     
     
      
     
     
     
     "
     
     
     
     224.1.1.3
     
     
     
     "
     
     
     
     ;

     
     
     
     int
     
     
     
      port 
     
     
     
     =
     
     
     
      
     
     
     
     12345
     
     
     
     ;


     
     
     
     int
     
     
     
      main(
     
     
     
     int
     
     
     
      argc, 
     
     
     
     char
     
     
     
     *
     
     
     
      argv[])
{
 
     
     
     
     int
     
     
     
      loop 
     
     
     
     =
     
     
     
      
     
     
     
     1
     
     
     
     ;
 
     
     
     
     /*
     
     
     
      多播循环 
     
     
     
     */
     
     
     
     
 
     
     
     
     int
     
     
     
      iter 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ;
 
     
     
     
     int
     
     
     
      from_len;
 
     
     
     
     char
     
     
     
      buffer[BUF_SIZE];
 
     
     
     
     int
     
     
     
      socket_descriptor;
 
     
     
     
     struct
     
     
     
      ip_mreq command;
 
     
     
     
     struct
     
     
     
      sockaddr_in loc;
 
     
     
     
     struct
     
     
     
      sockaddr_in rem;

 
     
     
     
     int
     
     
     
      rec_len 
     
     
     
     =
     
     
     
     0
     
     
     
     ;
 
     
     
     
     int
     
     
     
      ptr_point 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ;
 size_t bytes_written 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ;
 
     
     
     
     int
     
     
     
      loop_times 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ;

 
     
     
     
     int
     
     
     
      rcv_port_0 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ;
 
     
     
     
     int
     
     
     
      rcv_port_1 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ;
 
     
     
     
     int
     
     
     
      first 
     
     
     
     =
     
     
     
      
     
     
     
     0
     
     
     
     ;

#ifdef _WIN32
 WSADATA wsaData;

 
     
     
     
     if
     
     
     
     ( WSAStartup(MAKEWORD(
     
     
     
     2
     
     
     
     ,
     
     
     
     2
     
     
     
     ), 
     
     
     
     &
     
     
     
     wsaData) 
     
     
     
     !=
     
     
     
      
     
     
     
     0
     
     
     
      )
 {
 printf(
     
     
     
     "
     
     
     
     Error in WSAStartup/n
     
     
     
     "
     
     
     
     );
 exit(
     
     
     
     1
     
     
     
     );
 }

     
     
     
     #endif
     
     
     
     

 
     
     
     
     if
     
     
     
      (argv[
     
     
     
     1
     
     
     
     ])
 {
 host_name 
     
     
     
     =
     
     
     
      argv[
     
     
     
     1
     
     
     
     ];
 printf(
     
     
     
     "
     
     
     
     %s /n
     
     
     
     "
     
     
     
     , host_name);
 }
 
     
     
     
     if
     
     
     
      (argv[
     
     
     
     2
     
     
     
     ])
 {
 port 
     
     
     
     =
     
     
     
      atoi(argv[
     
     
     
     2
     
     
     
     ]);
 printf(
     
     
     
     "
     
     
     
     %d /n
     
     
     
     "
     
     
     
     , port);
 }

 memset(
     
     
     
     &
     
     
     
     loc, 
     
     
     
     0
     
     
     
     , 
     
     
     
     sizeof
     
     
     
     (loc));
 loc.sin_family 
     
     
     
     =
     
     
     
      AF_INET;
//这个地方很重要，不然linux下就只能是broadcast；所以必须指定组播的地址；
     
     
     
     

     
     
     
      loc.sin_port 
     
     
     
     =
     
     
     
      htons(port);
     
     
     
     

     
     
     
      loc.sin_addr.s_addr 
     
     
     
     =
     
     
     
      inet_addr(host_name); 
     
     
     
     

 
     
     
     
     if
     
     
     
     ((socket_descriptor 
     
     
     
     =
     
     
     
      socket(AF_INET, SOCK_DGRAM, 
     
     
     
     0
     
     
     
     )) 
     
     
     
     ==
     
     
     
      
     
     
     
     -
     
     
     
     1
     
     
     
     )
 { 
 perror(
     
     
     
     "
     
     
     
     socket
     
     
     
     "
     
     
     
     );
 exit(EXIT_FAILURE);
 }

 
     
     
     
     /*
     
     
     
     can use the same port in the pc
     
     
     
     */
     
     
     
     
 loop 
     
     
     
     =
     
     
     
      
     
     
     
     1
     
     
     
     ;
 
     
     
     
     if
     
     
     
     (setsockopt(socket_descriptor, SOL_SOCKET, SO_REUSEADDR, 
     
     
     
     &
     
     
     
     loop, 
     
     
     
     sizeof
     
     
     
     (loop)) 
     
     
     
     <
     
     
     
      
     
     
     
     0
     
     
     
     )
 {
 perror(
     
     
     
     "
     
     
     
     setsockopt:SO_REUSEADDR./n
     
     
     
     "
     
     
     
     );
 exit(EXIT_FAILURE);
 }
     
     
     
     else
     
     
     
     
 {
 printf(
     
     
     
     "
     
     
     
     setsockopt:SO_REUSEADDR./n
     
     
     
     "
     
     
     
     );
 }
 loop 
     
     
     
     =
     
     
     
      
     
     
     
     0x1000000
     
     
     
     ;// 设置网络的接收buffer的大小
 
     
     
     
     if
     
     
     
     ( setsockopt( socket_descriptor, SOL_SOCKET, SO_RCVBUF, (
     
     
     
     void
     
     
     
      
     
     
     
     *
     
     
     
     ) 
     
     
     
     &
     
     
     
     loop, 
     
     
     
     sizeof
     
     
     
     ( loop ) ) 
     
     
     
     <
     
     
     
      
     
     
     
     0
     
     
     
      )
 {
 perror(
     
     
     
     "
     
     
     
     setsockopt:SO_RCVBUF./n
     
     
     
     "
     
     
     
     );
 exit(EXIT_FAILURE);
 }

     
     
     
     
//由于在前面指定了组播的地址，但是在winodws和linux下不一样，就得这么处理，这个细节来之分析VLC源代码
#if defined( WIN32 ) || defined( UNDER_CE )

     
     
     
      
     
     
     
     /*
     
     
     
     
 * Under Win32 and for multicasting, we bind to INADDR_ANY.
 * This is of course a severe bug, since the socket would logically
 * receive unicast traffic, and multicast traffic of groups subscribed
 * to via other sockets. How this actually works in Winsock, I don't
 * know.
 
     
     
     
     */
     
     
     
     
 
     
     
     
     if
     
     
     
     ( IN_MULTICAST( ntohl( loc.sin_addr.s_addr ) ) )
 {
 
     
     
     
     struct
     
     
     
      sockaddr_in stupid 
     
     
     
     =
     
     
     
      loc;
 stupid.sin_addr.s_addr 
     
     
     
     =
     
     
     
      INADDR_ANY;

 
     
     
     
     if
     
     
     
     ( bind( socket_descriptor, (
     
     
     
     struct
     
     
     
      sockaddr 
     
     
     
     *
     
     
     
     )
     
     
     
     &
     
     
     
     stupid, 
     
     
     
     sizeof
     
     
     
     ( stupid ) ) 
     
     
     
     <
     
     
     
      
     
     
     
     0
     
     
     
      )
 {
 perror(
     
     
     
     "
     
     
     
     bind socket./n
     
     
     
     "
     
     
     
     );
 close( socket_descriptor );
 
     
     
     
     return
     
     
     
      
     
     
     
     0
     
     
     
     ;
 }
 }
 
     
     
     
     else
     
     
     
     

     
     
     
     #endif
     
     
     
      
 
     
     
     
     if
     
     
     
     (bind(socket_descriptor, (
     
     
     
     struct
     
     
     
      sockaddr 
     
     
     
     *
     
     
     
     )
     
     
     
     &
     
     
     
     loc, 
     
     
     
     sizeof
     
     
     
     (loc)) 
     
     
     
     <
     
     
     
      
     
     
     
     0
     
     
     
     )
 {
 perror(
     
     
     
     "
     
     
     
     bind socket./n
     
     
     
     "
     
     
     
     );
 exit(EXIT_FAILURE);
 }



 { //加入组播组，如果有多块网卡，可以用另一个变量来特别设置；
 printf(
     
     
     
     "
     
     
     
     %s,%d/n
     
     
     
     "
     
     
     
     , host_name, port);
 command.imr_multiaddr.s_addr 
     
     
     
     =
     
     
     
      inet_addr(host_name);
 command.imr_interface.s_addr 
     
     
     
     =
     
     
     
      htonl(INADDR_ANY);
 
     
     
     
     if
     
     
     
     (command.imr_multiaddr.s_addr 
     
     
     
     ==
     
     
     
      
     
     
     
     -
     
     
     
     1
     
     
     
     )
 { 
 perror(
     
     
     
     "
     
     
     
     224.1.1.3 not a legal multicast address./n
     
     
     
     "
     
     
     
     );
 exit(EXIT_FAILURE);
 }
 
     
     
     
     if
     
     
     
      (setsockopt(socket_descriptor, IPPROTO_IP, IP_ADD_MEMBERSHIP, 
     
     
     
     &
     
     
     
     command, 
     
     
     
     sizeof
     
     
     
     (command)) 
     
     
     
     <
     
     
     
      
     
     
     
     0
     
     
     
     )
 { 
 perror(
     
     
     
     "
     
     
     
     setsockopt:IP_ADD_MEMBERSHIP. error/n
     
     
     
     "
     
     
     
     );
 }
 }


 printf(
     
     
     
     "
     
     
     
     start reciving.../n
     
     
     
     "
     
     
     
     );


 from_len 
     
     
     
     =
     
     
     
      
     
     
     
     sizeof
     
     
     
     (rem);
 
     
     
     
     while
     
     
     
     (
     
     
     
     1
     
     
     
     )
 { 
 memset(
     
     
     
     &
     
     
     
     rem, 
     
     
     
     0
     
     
     
     , from_len); 
 memset(buffer, 
     
     
     
     0
     
     
     
     , BUF_SIZE);
 
     
     
     
     if
     
     
     
     ( (rec_len 
     
     
     
     =
     
     
     
      recvfrom(socket_descriptor, buffer, 
     
     
     
     sizeof
     
     
     
     (
     
     
     
     char
     
     
     
     ) 
     
     
     
     *
     
     
     
      BUF_SIZE, 
     
     
     
     0
     
     
     
     , (
     
     
     
     struct
     
     
     
      sockaddr 
     
     
     
     *
     
     
     
     )
     
     
     
     &
     
     
     
     rem, 
     
     
     
     &
     
     
     
     from_len)) 
     
     
     
     ==
     
     
     
      
     
     
     
     -
     
     
     
     1
     
     
     
     ) {
 perror(
     
     
     
     "
     
     
     
     recvfrom./n
     
     
     
     "
     
     
     
     ); 
 }

 printf( 
     
     
     
     "
     
     
     
     From host:%s port:%d, len: %d/n
     
     
     
     "
     
     
     
     , inet_ntoa(rem.sin_addr), ntohs(rem.sin_port), rec_len); 
 }
 
     
     
     
     if
     
     
     
     (setsockopt(socket_descriptor, IPPROTO_IP, IP_DROP_MEMBERSHIP, 
     
     
     
     &
     
     
     
     command, 
     
     
     
     sizeof
     
     
     
     (command)) 
     
     
     
     <
     
     
     
      
     
     
     
     0
     
     
     
     ) {
 perror(
     
     
     
     "
     
     
     
     setsockopt:IP_DROP_MEMBERSHIP./n
     
     
     
     "
     
     
     
     );
 } 
 closesocket(socket_descriptor);
 exit(EXIT_SUCCESS);
}

    
    
    
    

注：
1.在windows中不需要特殊的设置网络；
2.在Linux下得特别注意网络的设置，有下面几个环节：
1）查看内核模块，是否已经加载了multicast支持；这个可以通过 在src目录下面 make menuconfig 查看ip 设置栏目看到；
2）查看网络是否已经加载了multicast支持；命令：ip a 可以看到现在网络支持的各个功能；
3）添加multicast 网络路由：net add -net 224.0.0.0 netmask 240.0.0.0 dev eth0
这样才能启动网络的multicast路由支持，不然只能当作broadcast处理。