（1）网络编程之客户端模型

最新推荐文章于 2025-12-08 13:57:11 发布

原创最新推荐文章于 2025-12-08 13:57:11 发布 · 870 阅读

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#编程 #网络 #struct #internet #ubuntu #socket

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本文介绍了一个简单的TCP客户端程序，该程序使用C语言实现，并通过socket API连接到指定的IP地址和端口，接收并打印服务器响应。示例展示了如何创建socket、设置服务器地址并建立连接。

/* Internet address. */
struct in_addr {
	__u32	s_addr;
};

/* Structure describing an Internet (IP) socket address. */
#define __SOCK_SIZE__	16		/* sizeof(struct sockaddr)	*/
struct sockaddr_in {
  sa_family_t		sin_family;	/* Address family		*/
  unsigned short int	sin_port;	/* Port number			*/
  struct in_addr	sin_addr;	/* Internet address		*/

  /* Pad to size of `struct sockaddr'. */
  unsigned char		__pad[__SOCK_SIZE__ - sizeof(short int) -
			sizeof(unsigned short int) - sizeof(struct in_addr)];
};

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

#define RECV_BUF_SIZE 1024

int main(int argc, char **argv)
{
	int sockfd = 0;
	int ret = 0;
	char recvbBuffer[RECV_BUF_SIZE] = {0};
	struct sockaddr_in serverAddr;

	memset(&serverAddr, 0, sizeof(struct sockaddr_in));

	if (argc != 3)
	{
		fprintf(stderr, "Usage: %s host port msg...\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if (sockfd < 0)
	{
		fprintf(stderr, "Create socket fail\n");
		exit(EXIT_FAILURE);
	}

	serverAddr.sin_family = AF_INET;
	serverAddr.sin_port = htons(atoi(argv[2]));
	ret = inet_aton(argv[1], (struct in_addr *)(&serverAddr.sin_addr.s_addr));
	if (0 == ret)
	{
		fprintf(stderr, "Server address %s error\n", argv[1]);
		exit(EXIT_FAILURE);
	}

	ret = connect(sockfd, (struct sockaddr *)(&serverAddr), sizeof(serverAddr));
	if (ret != 0)
	{
		fprintf(stderr, "Connect server %s:%d fail\n", argv[1], atoi(argv[2]));
		exit(EXIT_FAILURE);
	}

	recv(sockfd, recvbBuffer, RECV_BUF_SIZE, 0);
	printf("%s", recvbBuffer);
	close(sockfd);

	return 0;
}

root@ubuntu:~/network_program/simple_client# ./a.out 127.0.0.1 21
220 (vsFTPd 2.2.2)
root@ubuntu:~/network_program/simple_client# ./a.out 127.0.0.1 22
SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7
root@ubuntu:~/network_program/simple_client# ./a.out 127.0.0.1 23
Connect server 127.0.0.1:23 fail