Linux Socket C語言網路程式設計：TCP Socket

/*
 * config.h 包含該tcp/ip套接字程式設計所需要的基本標頭檔案，與server.c client.c位於同一目錄下
*/

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

const int MAX_LINE = 2048;
const int PORT = 6000;
const int BACKLOG = 10;
const int LISTENQ = 6666;
const int MAX_CONNECT = 20;

/*
 * server.c為伺服器端程式碼
*/

#include "config.h"

int main(int argc , char **argv)
{
	/*宣告伺服器地址和客戶連結地址*/
	struct sockaddr_in servaddr , cliaddr;

	/*宣告伺服器監聽套接字和客戶端連結套接字*/
	int listenfd , connfd;
	pid_t childpid;

	/*宣告緩衝區*/
	char buf[MAX_LINE];

	socklen_t clilen;

	/*(1) 初始化監聽套接字listenfd*/
	if((listenfd = socket(AF_INET , SOCK_STREAM , 0)) < 0)
	{
		perror("socket error");
		exit(1);
	}//if

	/*(2) 設定伺服器sockaddr_in結構*/
	bzero(&servaddr , sizeof(servaddr));

	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY); //表明可接受任意IP地址
	servaddr.sin_port = htons(PORT);

	/*(3) 繫結套接字和埠*/
	if(bind(listenfd , (struct sockaddr*)&servaddr , sizeof(servaddr)) < 0)
	{
		perror("bind error");
		exit(1);
	}//if

	/*(4) 監聽客戶請求*/
	if(listen(listenfd , LISTENQ) < 0)
	{
		perror("listen error");
		exit(1);
	}//if

	/*(5) 接受客戶請求*/
	for( ; ; )
	{
		clilen = sizeof(cliaddr);
		if((connfd = accept(listenfd , (struct sockaddr *)&cliaddr , &clilen)) < 0 )
		{
			perror("accept error");
			exit(1);
		}//if

		//新建子程式單獨處理連結
		if((childpid = fork()) == 0) 
		{
			close(listenfd);
			//str_echo
			ssize_t n;
			char buff[MAX_LINE];
			while((n = read(connfd , buff , MAX_LINE)) > 0)
			{
				write(connfd , buff , n);
			}
			exit(0);
		}//if
		close(connfd);
	}//for
	
	/*(6) 關閉監聽套接字*/
	close(listenfd);
}

/*
 * client.c為客戶端程式碼
*/

#include "config.h"

/*readline函式實現*/
ssize_t readline(int fd, char *vptr, size_t maxlen)
{
	ssize_t	n, rc;
	char	c, *ptr;

	ptr = vptr;
	for (n = 1; n < maxlen; n++) {
		if ( (rc = read(fd, &c,1)) == 1) {
			*ptr++ = c;
			if (c == '\n')
				break;	/* newline is stored, like fgets() */
		} else if (rc == 0) {
			*ptr = 0;
			return(n - 1);	/* EOF, n - 1 bytes were read */
		} else
			return(-1);		/* error, errno set by read() */
	}

	*ptr = 0;	/* null terminate like fgets() */
	return(n);
}


int main(int argc , char ** argv)
{
	/*宣告套接字和連結伺服器地址*/
	int sockfd;
	struct sockaddr_in servaddr;

	/*判斷是否為合法輸入*/
	if(argc != 2)
	{
		perror("usage:tcpcli <IPaddress>");
		exit(1);
	}//if

	/*(1) 建立套接字*/
	if((sockfd = socket(AF_INET , SOCK_STREAM , 0)) == -1)
	{
		perror("socket error");
		exit(1);
	}//if

	/*(2) 設定連結伺服器地址結構*/
	bzero(&servaddr , sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(PORT);
	if(inet_pton(AF_INET , argv[1] , &servaddr.sin_addr) < 0)
	{
		printf("inet_pton error for %s\n",argv[1]);
		exit(1);
	}//if

	/*(3) 傳送連結伺服器請求*/
	if( connect(sockfd , (struct sockaddr *)&servaddr , sizeof(servaddr)) < 0)
	{
		perror("connect error");
		exit(1);
	}//if

	/*(4) 訊息處理*/
	char sendline[MAX_LINE] , recvline[MAX_LINE];
	while(fgets(sendline , MAX_LINE , stdin) != NULL)	
	{
		write(sockfd , sendline , strlen(sendline));

		if(readline(sockfd , recvline , MAX_LINE) == 0)
		{
			perror("server terminated prematurely");
			exit(1);
		}//if

		if(fputs(recvline , stdout) == EOF)
		{
			perror("fputs error");
			exit(1);
		}//if
	}//while

	/*(5) 關閉套接字*/
	close(sockfd);
}