群播技術

群播:
是指在發送者和每一個接收者之間實現點對多點網路連接
實例操作
實現一個基於C/S模式的群播通信,伺服器程式負責建立群播組,並提供一個鍵盤輸入介面,輸入的資訊向組內成員群播發送;客戶端加入群播組,接收伺服器的資訊並顯示,若發現資訊中包含quit則退出程式
1.伺服器程式

#include "stdio.h"
#include "sys/socket.h"
#include "netinet/in.h"
#include "arpa/inet.h"
#include "netdb.h"
#include "unistd.h"
#include "stdlib.h"

int main(void)
{    
 int server_socket;  
 struct sockaddr_in address;  

        server_socket = socket(AF_INET, SOCK_DGRAM, 0);  
 if (server_socket < 0) 
 {      
  perror("socket"); 
  return 0; 
 }   

 memset(&address, 0, sizeof(address));   
 address.sin_family = AF_INET;  
 address.sin_addr.s_addr = inet_addr("224.0.0.1"); 
 address.sin_port = htons(5555);  

 while(1)
 { 
  char buf[200];
  printf("input your word:>");
  scanf("%s",buf);
  if(sendto(server_socket, buf,sizeof(buf), 0,(struct sockaddr *)&address, sizeof(address)) < 0) 
  {  
   perror("sendto");  
   return ;
  }   
 }  
}


2.客戶端程式

#include "stdio.h"
#include "sys/socket.h"
#include "netinet/in.h"
#include "arpa/inet.h"
#include "netdb.h"
#include "unistd.h"
#include "stdlib.h"

int main(void)
{ 
 struct ip_mreq multiaddress;  
 int serveraddress_len; 
 int client_socket;
 struct sockaddr_in serveraddress;
 
 /*bzero(&serveraddress, sizeof(serveraddress));*/
 memset(&serveraddress, 0, sizeof(serveraddress));
 serveraddress.sin_family = AF_INET;
 serveraddress.sin_addr.s_addr = htonl(INADDR_ANY);
 serveraddress.sin_port = htons(5555);
 if((client_socket = socket(PF_INET, SOCK_DGRAM, 0)) < 0) 
 { 
  perror("socket");
  return 0;
 }
 
 int opt = 1;
 if(setsockopt(client_socket, SOL_SOCKET, SO_REUSEADDR,&opt, sizeof(opt)) < 0)
 { 
  perror("setsockopt:SO_REUSEADDR");
  return 0;
 }
 if(bind(client_socket, (struct sockaddr *)&serveraddress, sizeof(serveraddress)) < 0)
 {
  perror("bind"); 
  return 0;
    }

 // 婓肮珨跺翋儂奻輛俴嫘畦扢离杶諉諳
 multiaddress.imr_multiaddr.s_addr = inet_addr("224.0.0.1"); 
 multiaddress.imr_interface.s_addr = htonl(INADDR_ANY);
 
 // 樓嫘畦郪
 if (setsockopt(client_socket,IPPROTO_IP,IP_ADD_MEMBERSHIP,&multiaddress, sizeof(multiaddress)) < 0)
 {   
  perror("IP_ADD_MEMBERSHIP");
  return 0;
    } 

 while(1) 
 {    
  char buf[200];
  serveraddress_len = sizeof(serveraddress); 
  if(recvfrom(client_socket, buf, 200, 0, (struct sockaddr *)&serveraddress, &serveraddress_len) < 0) 
  { 
   perror("recvfrom");   
  }  
  printf("msg from server: %s\n", buf);

  if(strcmp(buf,"quit") == 0)
  {   
   if(setsockopt(client_socket, IPPROTO_IP, IP_DROP_MEMBERSHIP,&multiaddress, sizeof(multiaddress)) < 0) 
   { 
    perror("setsockopt:IP_DROP_MEMBERSHIP"); 
   }   
   close(client_socket); 
   return 0;
  }
 }  
}