学步园

这里练习用数据报套接字来通讯。

listener.c

// 数据报套接字服务器(listener.c)：在指定端口监听，收到数据报后关闭连接

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>

#define MYPORT 5000
#define MAXBUFLEN 100

int main(int argc, char *argv[])
{
	int sock_fd;
	struct sockaddr_in my_addr;
	struct sockaddr_in their_addr;
	int addr_len, numbytes;
	char buf[MAXBUFLEN];

	if((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
	{
		perror("socket");
		return 1;
	}
	my_addr.sin_family = AF_INET;
	my_addr.sin_port = htons(MYPORT);
	my_addr.sin_addr.s_addr = INADDR_ANY;	// 自动设置为自己的IP
	bzero(&(my_addr.sin_zero), 8);			// 将结构的其余空间清零

	if(bind(sock_fd, (struct sockaddr*)&my_addr, sizeof(struct sockaddr)) == -1)
	{
		perror("bind");
		return 1;
	}
	addr_len = sizeof(struct sockaddr);
	if((numbytes = recvfrom(sock_fd, buf, MAXBUFLEN, 0, (struct sockaddr*)&their_addr, &addr_len)) == -1)
	{
		perror("recvfrom");
		return 1;
	}
	close(sock_fd);
	printf("got packet from %s\n", inet_ntoa(their_addr.sin_addr));
	printf("packet is %d bytes long\n", numbytes);
	buf[numbytes] = 0;
	printf("packet contains [%s]\n", buf);

	return 0;
}

talker.c

// 数据报套接字客户端(talker.c)：向指定端口发送数据后关闭连接

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define MYPORT 5000

int main(int argc, char *argv[])
{
	int sock_fd, numbytes;
	struct sockaddr_in their_addr;
	struct hostent *he;

	if(argc < 3)
	{
		fprintf(stderr, "Usage: %s <hostname> <message>\n", argv[0]);
		return 1;
	}
	if((he = gethostbyname(argv[1])) == NULL)
	{
		herror("gethostbyname");
		return 1;
	}
	if((sock_fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
	{
		perror("socket");
		return 1;
	}

	their_addr.sin_family = AF_INET;
	their_addr.sin_port = htons(MYPORT);
	their_addr.sin_addr = *((struct in_addr*)he->h_addr);
	bzero(&(their_addr.sin_zero), 8);

	if((numbytes = sendto(sock_fd, argv[2], strlen(argv[2]), 0, (struct sockaddr*)&their_addr, sizeof(struct sockaddr))) == -1)
	{
		perror("sendto");
		return 1;
	}
	close(sock_fd);
	printf("sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));

	return 0;
}