udpserver.c

一个简单的udp通讯程序

#include <netinet/in.h>  
#include <sys/socket.h> 
#include <arpa/inet.h> 
#include <unistd.h> 
#include <sys/types.h>
#include <stdio.h>
int main()
{
        int sock;
        int clientlen=0;
	sock=socket(AF_INET,SOCK_DGRAM,0);
        struct sockaddr_in client;
        struct sockaddr_in server;
        bzero(&server,sizeof(server));
        server.sin_family=AF_INET;
        server.sin_addr.s_addr=inet_addr("10.1.0.235");
        server.sin_port=htons(9999);
        bind(sock,(struct sockaddr*)&server,sizeof(server));
	fd_set rdset;
        clientlen=sizeof(client);
        while(1)
	{
	   FD_ZERO(&rdset);
	   FD_SET(sock,&rdset);
           int result;
	   result=select(sock+1,&rdset,NULL,NULL,NULL);
	   if(result<0)
		   break;
	   else if(result==0)
		   continue;
	   if(FD_ISSET(sock,&rdset))
	   {
	       char recvbuf[100]="\0";
		clientlen = sizeof(client);
	       recvfrom(sock,recvbuf,sizeof(recvbuf),0,(struct sockaddr*)&client,&clientlen);
               printf("%s:%d\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));
               printf("receive is %s", recvbuf);
               char sendbuf[100]="hello";
               sendto(sock,sendbuf,sizeof(sendbuf),0,(struct sockaddr*)&client,clientlen);
	   }  
	}  
}