UDPserver.c

/**********UDP服务端程序UDPserver.c***********/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

#define SERVER_PORT 8888
#define MAX_MSG_SIZE 1024

void udps_respon(int sockfd) {
	struct sockaddr_in addr;
	unsigned int addrlen;
	int n;
	char msg[MAX_MSG_SIZE];

	while(1) {
	// 从网络上读,写到网络上去
		// 初始化addr长度!
		addrlen = sizeof(addr);
		if((n = recvfrom(sockfd,msg,MAX_MSG_SIZE,0,
			(struct sockaddr *)&addr,&addrlen)) < 0) {
			fprintf(stderr,"Recveive packahe error:%s",
				strerror(errno));
			continue;
		}
		msg[n - 1] = '\0';
		// 显示服务器端已经收到了信息
		fprintf(stdout,"I have received %s from %s\n",msg,
			inet_ntoa(addr.sin_addr));
		sendto(sockfd,msg,n,0,(struct sockaddr *)&addr,addrlen);
	}
}

int main(void) {
	int sockfd;
	struct sockaddr_in addr;
	sockfd = socket(AF_INET,SOCK_DGRAM,0);
	if(sockfd < 0) {
		fprintf(stderr,"Socket Error:%s\n",strerror(errno));
		exit(1);
	}

	bzero(&addr,sizeof(struct sockaddr_in));
	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = htonl(INADDR_ANY);
	addr.sin_port = htons(SERVER_PORT);

	if(bind(sockfd,(struct sockaddr *)&addr,
		sizeof(struct sockaddr_in)) < 0) {
		fprintf(stderr,"Bind Error:%s\n",strerror(errno));
		exit(1);
	}

	udps_respon(sockfd);
	close(sockfd);
	exit(1);
}