mthser.c

简单FTP多进程服务器示例程序 供初学者学习使用

	#include <stdio.h>          
	#include <strings.h>         
	#include <unistd.h>         
	#include <sys/types.h> 
	#include <sys/socket.h> 
	#include <netinet/in.h> 
	#include <arpa/inet.h>

	#define PORT 1234   
	#define BACKLOG 5   
	#define MAXDATASIZE 1000  
	void process_cli(int connectfd, struct sockaddr_in client);

	main() 
	{ 
		int listenfd, connfd; 
		pid_t pid;
		struct sockaddr_in server; 
		struct sockaddr_in client; 
		int len; 
	
		if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
                {
	   		perror("Creating socket failed.");
	   		exit(1);
	   	}
		int opt = SO_REUSEADDR;
		setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
		bzero(&server,sizeof(server));
		server.sin_family=AF_INET; 
		server.sin_port=htons(PORT); 
		server.sin_addr.s_addr = htonl(INADDR_ANY); 
		if (bind(listenfd, (struct sockaddr *)&server, sizeof(server)) == -1) 
  		{ 
	   		perror("Bind() error.");
	   		exit(1); 
	  	 }	    
		if(listen(listenfd,BACKLOG) == -1)
		{  
	   		perror("listen() error\n"); 
	   		exit(1); 
                }
		len=sizeof(client); 
		while(1)
		{
	 		if ((connfd = accept(listenfd,(struct sockaddr *)&client,&len))==-1) 
			{
	 			  perror("accept() error\n"); 
	   		          exit(1); 
	   		} 
			if ((pid=fork())>0) 
			{
	   			close(connfd);
	   			continue;
	   		}else if (pid==0) {
	   			close(listenfd);
	   			process_cli(connfd, client);
	   			exit(0);     
	   		}else {
	   			printf("fork() error\n");
	   			exit(0);
	   		}
		}
		close(listenfd);   
	} 

	void process_cli(int connfd, struct sockaddr_in client)
	{
		int num;
		char recvbuf[MAXDATASIZE], sendbuf[MAXDATASIZE], cli_name[MAXDATASIZE];
		printf("You got a connection from %s.  ",inet_ntoa(client.sin_addr) );
		num = recv(connfd, cli_name, MAXDATASIZE,0);
		if (num == 0) 
 		{
	  		close(connfd);
		   	printf("Client disconnected.\n");
		   	return;
	   	}
		cli_name[num - 1] = '\0';
		printf("Client's name is %s.\n",cli_name);

		while (num = recv(connfd, recvbuf, MAXDATASIZE,0)) 
		{
	   		recvbuf[num] = '\0';
	   		printf("Received client( %s ) message: %s",cli_name, recvbuf);
	   		int i = 0;
	   		for (i=0; i < num - 1; i++) 
	   		{
	   			if((recvbuf[i]>='a'&&recvbuf[i]<='z')||(recvbuf[i]>='A'&&recvbuf[i]<='Z'))
	   			{
	      				recvbuf[i] = recvbuf[i] + 3;
	      				if((recvbuf[i]>'Z'&&recvbuf[i]<='Z'+3)||(recvbuf[i]>'z'))
	      					recvbuf[i] = recvbuf[i] - 26;
	      				sendbuf[i] = recvbuf[i];	   	   		
	      			}
	   		}
	  		 sendbuf[num - 1] = '\0';
	   		send(connfd,sendbuf,strlen(sendbuf),0); 
	   	}
		close(connfd); 
	}