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网络编程之getsockname、getpeername、gethostbyname函数 gethostbyname()

admin 11月 13, 2020 0

网络编程之getsockname、getpeername、gethostbyname函数

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#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
#define ERR_EXIT(m) 
	do { 
		perror(m); 
		exit(EXIT_FAILURE); 
	} while(0) 
struct  {
	int len;
	char buf[1024];
};
int main() {
	int sockfd;
	if ((sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
		ERR_EXIT("socket");
	}
	struct sockaddr_in serveraddr;
	memset(&serveraddr, 0, sizeof(serveraddr));
	serveraddr.sin_family = AF_INET;
	serveraddr.sin_port = htons(5534);
	serveraddr.sin_addr.s_addr = inet_addr("127.0.0.1");
	if (connect(sockfd, (struct sockaddr*)&serveraddr, sizeof(serveraddr)) < 0) {
		ERR_EXIT("connect");
	}
	struct sockaddr_in addr;
	int len = sizeof(addr);
	if (getsockname(sockfd, (struct sockaddr*)&addr, &len) < 0) {
		ERR_EXIT("getsockname");
	}
	printf("ip=%s, port=%dn", inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
	struct sockaddr_in peeraddr;
	int peerlen = sizeof(peeraddr);
	if (getpeername(sockfd, (struct sockaddr*)&peeraddr, &peerlen) < 0) {
		ERR_EXIT("getsockname");
	}
	printf("ip=%s, port=%dn", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port));
	struct  send_packet;
	struct  recv_packet;
	
	while (fgets(send_packet.buf, sizeof(send_packet.buf), stdin) != 0) {
		int n = strlen(send_packet.buf);
		send_packet.len = htonl(n);
		write(sockfd, &send_packet, 4+n);
		
		int ret;
		if ((ret = read(sockfd, &recv_packet, 4+n)) < 0) {
			ERR_EXIT("readn");
		} else if (ret == 0) {
			printf("server closen");
			break;
		}
		fputs(recv_packet.buf, stdout);
		memset(&send_packet, 0, sizeof(send_packet));
		memset(&recv_packet, 0, sizeof(recv_packet));
	}
	close(sockfd);
	return 0;
}

gethostbyname()

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#include <stdlib.h>
#include <unistd.h>
#include <netdb.h>
#include <arpa/inet.h>
#define ERR_EXIT(m) 
	do { 
		perror(m); 
		exit(EXIT_FAILURE); 
	}while(0)
int main() {
	char host[100] = {0};
	if (gethostname(host, sizeof(host)) < 0) {
		ERR_EXIT("gethostname");
	}
	struct hostent *hp;
	if ((hp = gethostbyname(host)) == NULL) {
		ERR_EXIT("gethostbyname");
	}
	int i=0;
	while(hp->h_addr_list[i] != NULL) {
		printf("%sn", inet_ntoa(*(struct in_addr*)hp->h_addr_list[i]));
		++i;
	}
	return 0;
}
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