server_stage5.c

/*
** server.c -- a stream socket server demo
*/

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

#define PORT "3519"  // the port users will be connecting to

#define BACKLOG 10	 // how many pending connections queue will hold

#define MAXDATASIZE 100 // max number of bytes we can get at once 



void sigchld_handler(int s)
{
	(void)s; // quiet unused variable warning

	// waitpid() might overwrite errno, so we save and restore it:
	int saved_errno = errno;

	while(waitpid(-1, NULL, WNOHANG) > 0);

	errno = saved_errno;
}


// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
	if (sa->sa_family == AF_INET) {
		return &(((struct sockaddr_in*)sa)->sin_addr);
	}

	return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void)
{
	int sockfd, new_fd;  // listen on sock_fd, new connection on new_fd
	struct addrinfo hints, *servinfo, *p;
	struct sockaddr_storage their_addr; // connector's address information
	socklen_t sin_size;
	struct sigaction sa;
	int yes=1;
	char s[INET6_ADDRSTRLEN];
	int rv;
	char command;
   int my_fd[2];
   char new_buffer[MAXDATASIZE];
   char filename[MAXDATASIZE];


	memset(&hints, 0, sizeof hints);
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_flags = AI_PASSIVE; // use my IP

	if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
		return 1;
	}

	// loop through all the results and bind to the first we can
	for(p = servinfo; p != NULL; p = p->ai_next) {
		if ((sockfd = socket(p->ai_family, p->ai_socktype,
				p->ai_protocol)) == -1) {
			perror("server: socket");
			continue;
		}

		if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
				sizeof(int)) == -1) {
			perror("setsockopt");
			exit(1);
		}

		if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
			close(sockfd);
			perror("server: bind");
			continue;
		}

		break;
	}

	freeaddrinfo(servinfo); // all done with this structure

	if (p == NULL)  {
		fprintf(stderr, "server: failed to bind\n");
		exit(1);
	}

	if (listen(sockfd, BACKLOG) == -1) {
		perror("listen");
		exit(1);
	}

	sa.sa_handler = sigchld_handler; // reap all dead processes
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGCHLD, &sa, NULL) == -1) {
		perror("sigaction");
      
		exit(1);
	}

	printf("server: waiting for connections...\n");

	while(1) {  // main accept() loop
		sin_size = sizeof their_addr;
		new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
		if (new_fd == -1) {
			perror("accept");
			continue;
		}

      recv(new_fd, new_buffer, MAXDATASIZE, 0);
      sscanf(new_buffer, "%c %s", &command, filename);

		inet_ntop(their_addr.ss_family,
			get_in_addr((struct sockaddr *)&their_addr),
			s, sizeof s);
		
      switch(command){
         case 'l':
		      if (!fork()) { // this is the child process
			      dup2(new_fd,1);
            }
            execl("/usr/bin/ls", "ls", (char*)NULL);
            break;
        case 'q':
            close(new_fd);
            exit(0);
        case 'c':
            if(!fork()){
               //FILE* fp = NULL;
               //fp = fopen(filename, "r");
               int fp = access(filename, F_OK);
               if( fp == -1)//NULL )
                  send(new_fd, "File Does not Exist", 23, 0);
               else{
                  //fclose(fp);
                  send(new_fd, "File Exists", 23, 0);
               }
               close(new_fd);
            }
            
            //break;
            
/*        case 'p':
            if(!fork()){
               dup2(new_fd, 1);
               execl("/usr/bin/cat", "cat", filename, (char*)NULL);
               close(new_fd);
            }
            */
      }
		close(new_fd);  // parent doesn't need this
	}

	return 0;
}