udp_server.c

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


int main(int argc,char* argv[]){
	if(argc!=3){
		printf("Usage:%s [ip][port]\n",argv[0]);
		return 3;
	}
	//创建套接字
	int sock = socket(AF_INET,SOCK_DGRAM,0);
	if(sock<0){
		perror("socket");
		return 2;
	}
	//创建struct sockaddr_in结构体
	struct sockaddr_in local;
	local.sin_family = AF_INET;
	local.sin_port = htons(atoi(argv[2]));
	//将ip地址转换成四字节
	local.sin_addr.s_addr = inet_addr(argv[1]);
	//绑定
	if(bind(sock,(struct sockaddr*)&local,sizeof(local))<0){
		perror("bind");
		return 3;
	}
	char buf[1024];
	struct sockaddr_in client;
	while(1){
		socklen_t len =sizeof(client);
		size_t s = recvfrom(sock,buf,sizeof(buf)-1,0,(struct sockaddr*)&client,&len);
		if(s>0){
			buf[s] = 0;
			printf("[%s:%d]:%s\n",inet_ntoa(client.sin_addr),ntohs(client.sin_port),buf);
			sendto(sock,buf,strlen(buf),0,(struct sockaddr*)&client,sizeof(client));
		}
	}
}