prg6_3.c

Unix下用C语言进行网络编程的范例

// File: prg6_3.c
	#include <stdio.h>          /* These are the usual header files */ 
	#include <strings.h>          /* for bzero() */
	#include <unistd.h>         /* for close() */
	#include <sys/types.h> 
	#include <sys/socket.h> 
	#include <netinet/in.h> 
	#include <arpa/inet.h>

	#define PORT 1234   /* Port that will be opened */ 
	#define BACKLOG 2   /* Number of allowed connections */ 
	#define MAXDATASIZE 1000  
	void process_cli(int connectfd, sockaddr_in client);

	main() 
	{ 
	int listenfd, connectfd; /* socket descriptors */ 
	pid_t pid;
	struct sockaddr_in server; /* server's address information */ 
	struct sockaddr_in client; /* client's address information */ 
	int sin_size; 

	/* Create TCP socket  */
	if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
	   /* handle exception */
	   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(struct sockaddr)) == -1) { 
	   /* handle exception */
	   perror("Bind error.");
	   exit(1); 
	   }    

	if(listen(listenfd,BACKLOG) == -1){  /* calls listen() */ 
	   perror("listen() error\n"); 
	   exit(1); 
	   } 

	sin_size=sizeof(struct sockaddr_in); 

	while(1)
	{
	   /*accept connection */
	 if ((connectfd = accept(listenfd,(struct sockaddr *)&client,&sin_size))==-1) {
	   perror("accept() error\n"); 
	   exit(1); 
	   } 
	/*  Create child process to service client */
	if ((pid=fork())>0) {
	   /* parent process */
	   close(connectfd);
	   continue;
	   }
	else if (pid==0) {
	   /*child process*/
	   close(listenfd);
	   process_cli(connectfd, client);
	   exit(0);     
	   }
	else {
	   printf("fork error\n");
	   exit(0);
	   }
	}
	close(listenfd);   /* close listenfd */         
	} 

	void process_cli(int connectfd, 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) ); /* prints client's IP */ 
	/* Get client's name from client */
	num = recv(connectfd, cli_name, MAXDATASIZE,0);
	if (num == 0) {
	   close(connectfd);
	   printf("Client disconnected.\n");
	   return;
	   }
	cli_name[num - 1] = '\0';
	printf("Client's name is %s.\n",cli_name);

	while (num = recv(connectfd, recvbuf, MAXDATASIZE,0)) {
	   recvbuf[num] = '\0';
	   printf("Received client( %s ) message: %s",cli_name, recvbuf);
	   for (int i = 0; i < num - 1; i++) {
	      sendbuf[i] = recvbuf[num - i -2];
	      }
	   sendbuf[num - 1] = '\0';

	   send(connectfd,sendbuf,strlen(sendbuf),0); /* send to the client welcome message */ 
	   }
	close(connectfd); /*  close connectfd */ 
	}