Linux 网络编程: echo Service

前言

大病初愈，感谢某人的陪伴，感谢王乐庆同学和赵攀同学的细心照顾。原以为过了第八周就不忙了，却没想到还有明天的党章考试。还是写代码比背党章有意思~趁着服务器还没过期，赶紧把 echo 完成了。关于错误提示和连接 socket 的代码就不贴出来了。

服务器配置

vi /etc/xinetd.d/echo

把 disable = yes 改成 disable = no ，类似 time 服务，如果没有写的权限，就要 chmod，然后重启 xinetd 服务。

service xinetd restart

Client

UDPecho.c

/* UDPecho.c - main */

#include <sys/types.h>

#include <unistd.h>

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <errno.h>

#define	LINELEN		128

extern int	errno;

int UDPecho(const char *host, const char *service);

int	connectUDP(const char *host, const char *service);

int	errexit(const char *format, ...);

/*---------------------------------------------------------------------------

 * main - UDP client for ECHO service

 *---------------------------------------------------------------------------

 */

int main(int argc, char *argv[])

{

	char	*host = "localhost";	/* host to use if none supplied	*/

	char	*service = "echo";	/* default service name		*/

	int	s, n;			/* socket descriptor, read count*/

    char buf[LINELEN+1];

    int outchars, inchars;

	switch (argc) {

	case 1:

		host = "localhost";

		break;

	case 3:

		service = argv[2];

		/* FALL THROUGH */

	case 2:

		host = argv[1];

		break;

	default:

		fprintf(stderr, "usage: UDPecho [host [port]]\n");

		exit(1);

	}

    UDPecho(host, service);

    exit(0);

}

/*---------------------------------------------------------------------------

 * UDPecho - send input to ECHO service on specified host and print and reply

 *---------------------------------------------------------------------------

 */

int UDPecho(const char *host, const char *service)

{

    char buf[LINELEN+1];    /* buffer for one line of text */

    int s, nchars;    /* socket descriptor, read count */

    s = connectUDP(host, service);

    while (fgets(buf, sizeof(buf), stdin)) {

    //从命令行读入用户输入的字符

        buf[LINELEN] = '\0';    /* insure null-terminated */

        nchars = strlen(buf);

        (void) write(s, buf, nchars);

        //向网络中发送用户所输入的字符

        memset(buf, 0, LINELEN);

        if (read(s, buf, nchars) < 0) {

        //从网络中读取服务器所返回的的字符

            errexit("socket read failed: %s\n", strerror(errno));

        }

        fputs(buf, stdout);

    }

}

编译运行

然后不使用 xinetd 的自带服务，自己写服务器端的程序：

Server

UDPechod.c

/* UDPechod.c - main */

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <stdlib.h>

#include <stdio.h>

#include <time.h>

#include <string.h>

#include <errno.h>

extern int	errno;

#define	LINELEN		128

int UDPechod(const char *service);

int	passiveUDP(const char *service);

int	errexit(const char *format, ...);

/*------------------------------------------------------------------------

 * main - Iterative UDP server for ECHO service

 *------------------------------------------------------------------------

 */

int main(int argc, char *argv[])

{

	char	*service = "echo";	/* service name or port number	*/

	switch (argc) {

	case	1:

		break;

	case	2:

		service = argv[1];

		break;

	default:

		errexit("usage: UDPechod [port]\n");

	}

    UDPechod(service);

    exit(0);

}

int UDPechod(const char *service)

{

    struct sockaddr_in fsin;	/* the from address of a client	*/

    unsigned int	alen;		/* from-address length		*/

    char	buf[LINELEN+1];			/* "input" buffer */

    int	sock;			/* server socket		*/

    sock = passiveUDP(service);

    while (1) {

        alen = sizeof(fsin);

        if (recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr *)&fsin, &alen) < 0) {

        //从已连接的 socket 中获取传递过来的信息

            errexit("recvfrom: %s\n", strerror(errno));

        }

        (void) sendto(sock, &buf, sizeof(buf), 0, (struct sockaddr *)&fsin, sizeof(fsin));

        //将信息返回

    }

}

巴特西

Linux 网络编程: echo Service

前言

服务器配置

Client

编译运行

Server

编译运行

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