Linux UDP服务端客户端程序

服务端

#include<stdio.h>
#include<string.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<stdlib.h>
#include<netinet/in.h>
#include<arpa/inet.h>

#define PORT 1234
#define MAXDATASIZE 100

main()
{
   int sockfd;
   struct sockaddr_in server;
   struct sockaddr_in client;
   socklen_t addrlen;
   int num;
   char buf[MAXDATASIZE];

   if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) 
   {
	   perror("Creatingsocket failed.");
	   exit(1);
   }

   bzero(&server,sizeof(server));
   server.sin_family=AF_INET;
   server.sin_port=htons(PORT);
   server.sin_addr.s_addr= htonl (INADDR_ANY);
   if(bind(sockfd, (struct sockaddr *)&server, sizeof(server)) == -1)
   {
	   perror("Bind()error.");
	   exit(1);
   }   

   addrlen=sizeof(client);
   while(1)  
   {
		num =recvfrom(sockfd,buf,MAXDATASIZE,0,(struct sockaddr*)&client,&addrlen);                                   

   if (num < 0)
   {
	   perror("recvfrom() error\n");
	   exit(1);
   }

	   buf[num] = '\0';
	   printf("You got a message (%s%) from client.\nIt's ip is%s, port is %d.\n",buf,inet_ntoa(client.sin_addr),htons(client.sin_port)); 
	   sendto(sockfd,"Welcometo my server.\n",22,0,(struct sockaddr *)&client,addrlen);
	   if(!strcmp(buf,"bye"))
	   break;
   }
   close(sockfd);  
}

//客户端

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define PORT 1234
#define MAXDATASIZE 100

int main(int argc, char *argv[])
{
	int sockfd, num;
	char buf[MAXDATASIZE];

	struct hostent *he;
	struct sockaddr_in server,peer;

	if (argc !=3)
	{
		printf("Usage: %s <IP Address><message>\n",argv[0]);
		exit(1);
	}

	if ((he=gethostbyname(argv[1]))==NULL)
	{
		printf("gethostbyname()error\n");
		exit(1);
	}

	if ((sockfd=socket(AF_INET, SOCK_DGRAM,0))==-1)
	{
		printf("socket() error\n");
		exit(1);
	}

	bzero(&server,sizeof(server));
	server.sin_family = AF_INET;
	server.sin_port = htons(PORT);
	server.sin_addr= *((struct in_addr *)he->h_addr);
	sendto(sockfd, argv[2],strlen(argv[2]),0,(struct sockaddr *)&server,sizeof(server));
	socklen_t  addrlen;
	addrlen=sizeof(server);
	while (1)
	{
	if((num=recvfrom(sockfd,buf,MAXDATASIZE,0,(struct sockaddr *)&peer,&addrlen))== -1)
	{
		printf("recvfrom() error\n");
		exit(1);
	}
	if (addrlen != sizeof(server) ||memcmp((const void *)&server, (const void *)&peer,addrlen) != 0)
	{
		printf("Receive message from otherserver.\n");
		continue;
	}

	buf[num]='\0';
	printf("Server Message:%s\n",buf);
	break;
	}

	close(sockfd);
}

//示例
./client 127.0.0.1 hello
./server