udp_server.c

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

int main(int argc, char *argv[])
{
	int server_sockfd;
	int len;
	struct sockaddr_in my_addr; //服务器网络地址结构体
    struct sockaddr_in remote_addr; //客户端网络地址结构体
	int sin_size;
	char buf[BUFSIZ]; //数据传送的缓冲区
	memset(&my_addr, 0, sizeof(my_addr)); //数据初始化--清零
	my_addr.sin_family = AF_INET; //设置为IP通信
	my_addr.sin_addr.s_addr = INADDR_ANY; //服务器IP地址--允许连接到所有本地地址上
	my_addr.sin_port = htons(8001); //服务器端口号
	
	/* 创建服务器端套接字--IPv4协议，面向无连接通信，UDP协议 */
	if ( (server_sockfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0 )
	{  
		perror("socket");
		return 1;
	}
 
    /* 将套接字绑定到服务器的网络地址上 */
	if ( bind(server_sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) < 0 )
	{
		perror("bind");
		return 1;
	}

	sin_size = sizeof(struct sockaddr_in);
	printf("waiting for a packet...\n");
	
	/* 接收客户端的数据并将其发送给客户端--recvfrom是无连接的 */
	if( (len = recvfrom(server_sockfd, buf, BUFSIZ, 0, (struct sockaddr *)&remote_addr, &sin_size)) < 0 )
	{
		perror("recvfrom"); 
		return 1;
	}
	printf("received packet from %s:\n", inet_ntoa(remote_addr.sin_addr));
	buf[len] = '\0';
	printf("contents: %s\n",buf);
	close(server_sockfd);
        return 0;
}