udp的socket的helloworld

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[root@red54apple test]# cat udpclient.c 
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>

#define MAXLINE 80
#define SERV_PORT 8888

void do_cli(FILE *fp, int sockfd, struct sockaddr *pservaddr, socklen_t servlen)
{
		int n;
		char sendline[MAXLINE], recvline[MAXLINE + 1];

		/* connect to server */
		if(connect(sockfd, (struct sockaddr *)pservaddr, servlen) == -1)
		{
				perror("connect error");
				exit(1);
		}

		while(fgets(sendline, MAXLINE, fp) != NULL)
		{
				/* read a line and send to server */
				write(sockfd, sendline, strlen(sendline));
				/* receive data from server */
				n = read(sockfd, recvline, MAXLINE);
				if(n == -1)
				{
						perror("read error");
						exit(1);
				}
				recvline[n] = 0; /* terminate string */
				fputs(recvline, stdout);
		}
}

int main(int argc, char **argv)
{
		int sockfd;
		struct sockaddr_in servaddr;

		/* check args */
		if(argc != 2)
		{
				printf("usage: udpclient <IPaddress>\n");
				exit(1);
		}

		/* init servaddr */
		bzero(&servaddr, sizeof(servaddr));
		servaddr.sin_family = AF_INET;
		servaddr.sin_port = htons(SERV_PORT);
		if(inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0)
		{
				printf("[%s] is not a valid IPaddress\n", argv[1]);
				exit(1);
		}

		sockfd = socket(AF_INET, SOCK_DGRAM, 0);

		do_cli(stdin, sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

		return 0;
}
[root@red54apple test]#

[root@red54apple test]# cat udpserv.c 
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>

#define MAXLINE 80
#define SERV_PORT 8888

void do_echo(int sockfd, struct sockaddr *pcliaddr, socklen_t clilen)
{
		int n;
		socklen_t len;
		char mesg[MAXLINE];

		for(;;)
		{
				len = clilen;
				/* waiting for receive data */
				n = recvfrom(sockfd, mesg, MAXLINE, 0, pcliaddr, &len);
				/* sent data back to client */
				sendto(sockfd, mesg, n, 0, pcliaddr, len);
		}
}

int main(void)
{
		int sockfd;
		struct sockaddr_in servaddr, cliaddr;

		sockfd = socket(AF_INET, SOCK_DGRAM, 0); /* create a socket */

		/* init servaddr */
		bzero(&servaddr, sizeof(servaddr));
		servaddr.sin_family = AF_INET;
		servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
		servaddr.sin_port = htons(SERV_PORT);

		/* bind address and port to socket */
		if(bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1)
		{
				perror("bind error");
				exit(1);
		}

		do_echo(sockfd, (struct sockaddr *)&cliaddr, sizeof(cliaddr));

		return 0;
}
[root@red54apple test]# 


检查方法
netstat -ln|grep 8888