linux下socket编程-UDP

下面是UDP的服务器的代码：

/* server.c */
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ctype.h>
#include "wrap.h"
 
#define MAXLINE 80
#define SERV_PORT 8000
 
int main(void)
{
	struct sockaddr_in servaddr, cliaddr;
	socklen_t cliaddr_len;
	int sockfd;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN];
 
	int i, n;
 
	sockfd = wrap_socket(AF_INET, SOCK_DGRAM, 0);
 
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);
 
	wrap_bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr));
 
	printf("Accepting connections ...\n");
	while(1)
	{
		cliaddr_len = sizeof(cliaddr);
		n = recvfrom(sockfd, buf, MAXLINE, 0, (struct sockaddr *)&cliaddr, &cliaddr_len);
 
		if(n == -1)
		{
			perr_exit("recvfrom error");
		}
		printf("received from %s at port %d\n",
			inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
			ntohs(cliaddr.sin_port));
		for(i = 0; i < n; ++i)
		{
			buf[i] = toupper(buf[i]);
		}
 
		n = sendto(sockfd, buf, n, 0, (struct sockaddr *)&cliaddr, sizeof(cliaddr));
		if(n == -1)
			perr_exit("sendto error!");
	}
}

客户端代码：

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "wrap.h"
 
#define MAXLINE 80
#define SERV_PORT 8000
 
int main(int argc, char *argv[])
{
	struct sockaddr_in servaddr;
	int sockfd, n;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN];
	socklen_t servaddr_len;
 
	sockfd = wrap_socket(AF_INET, SOCK_DGRAM, 0);
 
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
	servaddr.sin_port = htons(SERV_PORT);
 
	while(fgets(buf, MAXLINE, stdin) != NULL)
	{
		n = sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *)&servaddr, sizeof(servaddr));
		if(n == -1)
			perr_exit("sendto error");
 
		n = recvfrom(sockfd, buf, MAXLINE, 0, NULL, 0);
		if(n == -1)
			perr_exit("recvfrom error");
 
		wrap_write(STDOUT_FILENO, buf, n);
	}
 
	wrap_close(sockfd);
	return 0;
}

由于server和client没有先建立连接然后通信的条件，所以server可以有并发能力。

用Ctrl+C关闭server，然后再运行server，client还能和server联系上。