udp_client.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 client_sockfd;
	int len;
    struct sockaddr_in remote_addr; //服务器端网络地址结构体
	int sin_size;
	char buf[BUFSIZ]; //数据传送的缓冲区

	memset(&remote_addr, 0, sizeof(remote_addr)); //数据初始化--清零
	remote_addr.sin_family = AF_INET; //设置为IP通信
	remote_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); //服务器IP地址
	remote_addr.sin_port = htons(8001); //服务器端口号

    /* 创建客户端套接字--IPv4协议，面向无连接通信，UDP协议 */
	if ( (client_sockfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0 )
	{  
		perror("socket");
		return 1;
	}

	strcpy(buf,"This is a test message");
	printf("sending: '%s'\n",buf);
	sin_size = sizeof(struct sockaddr_in);
	
	/* 向服务器发送数据包 */
	if ( (len = sendto(client_sockfd, buf, strlen(buf), 0, (struct sockaddr *)&remote_addr, sizeof(struct sockaddr))) < 0 )
	{
		perror("recvfrom"); 
		return 1;
	}

	close(client_sockfd);
	return 0;
}