client.c

linux upd套接字写的服务器客户端程序

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <errno.h>

#define RET_OK   0
#define RET_ERR -1

#define LISTEN_QUEUE_NUM 5
#define BUFFER_SIZE 256
#define ECHO_PORT 2029


int main(int argc, char *argv[])
{
	int sockfd, ret = RET_OK;
	struct sockaddr_in servaddr;
	struct hostent *server;

	char buffer[BUFFER_SIZE];

	if (argc < 2) {
		fprintf(stderr,"usage %s hostname\n", argv[0]);
		return RET_ERR;
	}
	if((server = gethostbyname(argv[1])) == NULL)
	{
		herror("gethostbyname. ");
		return RET_ERR;
	}

	if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
	{
		perror("ERROR opening socket");
		return RET_ERR;
	}
	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = *(uint32_t *)server->h_addr;
	servaddr.sin_port = htons((uint16_t)ECHO_PORT);

	while(1)
	{
		printf("Enter the message  : ");
		if(fgets(buffer, sizeof(buffer) - 1, stdin) == NULL)
		{
			break;
		}
		if((ret = sendto(sockfd, buffer ,strlen(buffer), 0, (struct sockaddr *)&servaddr, sizeof(servaddr))) < 0)
		{
			perror("ERROR writing to socket");
			break;
		}
		if((ret = recvfrom(sockfd, buffer, sizeof(buffer) - 1, 0, NULL, NULL)) < 0)
		{
			perror("ERROR reading from socket");
			break;
		}
		buffer[ret] = 0;
		printf("Server echo message: %s\n",buffer);
	}
	close(sockfd);
	return ret < 0 ? RET_ERR : RET_OK;
}