UNIX环境高级编程学习之第十六章网络IPC：套接字 – 简单UDP Socket 通信

/* User:Lixiujie         
 * Date:20101122
 * Desc:简单Udp通信，向其它连接过来的发送uptime信息。
 * File:udp_client1.c  
 * System:Ubuntu 64bit  
 * gcc udp_client1.c  udp_client1
 * udp_client1 0.0.0.0 7878
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>

#include <unistd.h>  

#include <sys/types.h> 
#include <sys/socket.h> /* socket bind listen connect accept send recv sendto recvfrom */
#include <arpa/inet.h>  /* htons ntohs htonl ntohl inet_addr inet_ntoa */
#include <netinet/in.h> /* sockaddr_in */

#define BUFLEN 128

/* create udp */
int initserver(int type, const struct sockaddr *addr, socklen_t alen, int qlen){
	int fd;
	int err = 0;
	/* 创建 */
	if ((fd = socket(addr->sa_family, type, 0)) < 0){
		return -1;
	}
	/* 绑定 */
	if (bind(fd, addr, alen) < 0){
		err = errno;
		goto errout;
	}
	/* 监听数 */
	if (SOCK_STREAM == type || SOCK_SEQPACKET == type){
		if (listen(fd, qlen) < 0) {
			err = errno;
			goto errout;
		}
	}
	return fd;
errout:
	close(fd);
	errno = err;
	return -1;
}

int main(int argc, char *argv[]){
	if (argc != 3){
		printf("arg err!/n");
		return -1;
	}
	int myfd, ret;
	FILE *fp;
	char szBuf[BUFLEN];
	struct sockaddr_in my_addr,you_addr;
	socklen_t alen = sizeof(struct sockaddr);
	/* 设置本身IP和端口 */
	memset((void *)&my_addr, 0, alen);
	my_addr.sin_family = AF_INET;
	my_addr.sin_addr.s_addr = inet_addr(argv[1]);
	my_addr.sin_port = htons(atoi(argv[2]));
	
	if ((myfd = initserver(SOCK_DGRAM, (struct sockaddr *)&my_addr, alen, 0)) > 0){
		while (1){
			alen = sizeof(struct sockaddr);
			memset((void *)&you_addr, 0 , alen);
			memset(szBuf, 0, BUFLEN);
			ret = recvfrom(myfd, szBuf, BUFLEN, 0,  (struct sockaddr*)&you_addr, &alen);
			if (ret < 0){
				printf("recvfrom err=%s!/n", strerror(errno));
				close(myfd);
				return -1;
			}
			printf("udp recvfrom:ip=%s, port=%d, data:%s /n", inet_ntoa(you_addr.sin_addr), ntohs(you_addr.sin_port), szBuf);
			if ((fp = popen("/usr/bin/uptime", "r")) == NULL){
				memset(szBuf, 0, BUFLEN);
				sprintf(szBuf, "error: %s/n", strerror(errno));
				sendto(myfd, szBuf, strlen(szBuf), 0, (struct sockaddr*)&you_addr, alen);
			}else{
				memset(szBuf, 0, BUFLEN);
				while (fgets(szBuf, BUFLEN, fp) != NULL){
					sendto(myfd, szBuf, strlen(szBuf), 0, (struct sockaddr*)&you_addr, alen);
					memset(szBuf, 0, BUFLEN);
				}
				pclose(fp);
			}
		}
	}else{
		printf("initserver err=%s!/n", strerror(errno));
		close(myfd);
		return -1;
	}
	close(myfd);
	return 0;
}