基于UDP的回声服务器/客户端

//服务器端代码：

#include 
#include 
#include 
#include 
#include 
#include 
#define MAXN 1024
void error_handling(const char *str)
{
	fputs(str,stderr);
	fputc('\n',stderr);
	exit(1);
}

int main(int argc,char *argv[])
{
	int serv_sock;
	int n=5,str_len;
	struct sockaddr_in serv_addr;
	struct sockaddr_in clnt_addr;
	socklen_t clnt_addr_size;
	char msg[MAXN];	
	if(argc!=2)
	{
		printf("Usage:%s \n",argv[0]);	
		exit(1);
	}
	serv_sock=socket(PF_INET,SOCK_DGRAM,0);		//第一步:注意是SOCK_DGRAM
	if(serv_sock==-1)
		error_handling("socket() error");
	
	memset(&serv_addr,0,sizeof(serv_addr));
	serv_addr.sin_family=AF_INET;
	serv_addr.sin_addr.s_addr=htonl(INADDR_ANY);
	serv_addr.sin_port=htons(atoi(argv[1]));
	
	if(bind(serv_sock,(struct sockaddr*)&serv_addr,sizeof(serv_addr))==-1)		//第二步
		error_handling("bind() error");
	
	while(n--)
	{
		clnt_addr_size=sizeof(clnt_addr);
		str_len=recvfrom(serv_sock,msg,MAXN,0,(struct sockaddr*)&clnt_addr,&clnt_addr_size);	//接收数据
		sendto(serv_sock,msg,str_len,0,(struct sockaddr*)&clnt_addr,clnt_addr_size);	//发送数据	
	}
	close(serv_sock);
	return 0;
}

//客户端代码：

#include 
#include 
#include 
#include 
#include 
#include 
#define MAXN 1024
void error_handling(const char *str)
{
	fputs(str,stderr);
	fputc('\n',stderr);
	exit(1);
}

int main(int argc,char *argv[])
{
	int clnt_sock,str_len;
	struct sockaddr_in serv_adr,from_adr;
	socklen_t from_adr_sz;
	char msg[]="HelloWorld";
	char store[1024];
	if(argc!=3)
	{
		printf("ERROR\n");
		exit(1);
	}
	clnt_sock=socket(PF_INET,SOCK_DGRAM,0);		//第一步
	if(clnt_sock==-1)
		error_handling("socket() error");
	
	memset(&serv_adr,0,sizeof(serv_adr));
	serv_adr.sin_family=AF_INET;
	serv_adr.sin_addr.s_addr=inet_addr(argv[1]);
	serv_adr.sin_port=htons(atoi(argv[2]));
	
	str_len=sendto(clnt_sock,msg,strlen(msg),0,(struct sockaddr*)&serv_adr,sizeof(serv_adr));	//发送数据
	from_adr_sz=sizeof(from_adr);
	recvfrom(clnt_sock,store,str_len,0,(struct sockaddr*)&from_adr,&from_adr_sz);	//接收数据
	store[str_len]='\0';
	printf("Message from server: %s\n",store);	
	close(clnt_sock);
	return 0;
}