Thread: socket program help

Hi,

I'm writing a client-server socket program. the client will be an instance of the well-known telnet application. i want to implement a simple authentication between the server and the client.
- the client should send this message (after the connection established): my password "anypassword"
and the server will check, if it's not the same password that's hardcoded in the server program, the server close connection.

so the client will be like that:

1.telnet server
2. got connected
3. provide password, if it's not coreect server close connection


here is my server application:

Code:

#include <unistd.h> 
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>
#include <ctype.h>
#include <time.h>
#define SERVERPORT 111              /* port used for the connection */  
#define QUEUE 5                       /* max # of queued connects */

int main(void)
{
    fd_set master;   // master file descriptor list
    fd_set read_fds; // temp file descriptor list for select()
    int fdmax;        // maximum file descriptor number
    int i , j;
    int nbytes;
     int s_listen,d_newconn;  
    int yes=1;
    struct sockaddr_in serveraddr;    /* server address */
    struct sockaddr_in clientaddr;    /* client address */
    struct sigaction sig;
    socklen_t sin_size;               /* Socket address length type */
    string buffer[256];
    
    FD_ZERO(&master);    // clear the master and temp sets
    FD_ZERO(&read_fds);    
 

    if ((s_listen = socket(AF_INET, SOCK_STREAM, 0)) == -1) {    /* create listen socket */
        perror("socket");
        exit(1);
    }

    /* set the options for the socket to allow reuse of a local port/address combination. */

    if (setsockopt(s_listen,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) {
        perror("setsockopt");
        exit(1);
    }
    
      memset(&(serveraddr.sin_zero), '\0', 8);  /* clear our address */
      serveraddr.sin_family = AF_INET;          /* Address Family */
      serveraddr.sin_port = htons(SERVERPORT);  /* Port number */
      /* a wild IP number to allow the system to pick the route to the remote service */
      serveraddr.sin_addr.s_addr = INADDR_ANY;  
     
      /* bind address to socket */
      if (bind(s_listen, (struct sockaddr *)&serveraddr, sizeof(struct sockaddr))  == -1) {
         perror("bind");
         exit(1);
      }

      /*listen*/ 
      if (listen(s_listen, QUEUE) == -1) {
         perror("listen");
         exit(1);
      }
    
// add the listener to the master set
    FD_SET(s_listen, &master);

    // keep track of the biggest file descriptor
    fdmax = s_listen; // so far, it's this one

    // main loop
    for(;;) {
        read_fds = master; // copy it
        if (select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1) {
            perror("select");
            exit(1);
        }

        // run through the existing connections looking for data to read
        for(i = 0; i <= fdmax; i++) {
            if (FD_ISSET(i, &read_fds)) { // we got one!!
                if (i == s_listen) {
                    // handle new connections
                    sin_size = sizeof(clientaddr);
                    if ((d_newconn = accept(s_listen, (struct sockaddr *)&clientaddr,
                                                               &sin_size)) == -1) { 
                        perror("accept");
                    } else {
                        FD_SET(d_newconn, &master); // add to master set
                        if (d_newconn > fdmax) {    // keep track of the maximum
                            fdmax = d_newconn;
                        }
                        printf("EDMTS SERVER: new connection from %s on "
                            "socket %d\n", inet_ntoa(clientaddr.sin_addr), d_newconn);
                    }
                } else {
                    // handle data from a client
                    if ((nbytes = recv(i, buffer, sizeof(buffer), 0)) <= 0) {
                        // got error or connection closed by client
                        if (nbytes == 0) {
                            // connection closed
                            printf("SERVER: socket %d hung up\n", i);
                        } else {
                            perror("recv");
                        }
                        close(i); // bye!
                        FD_CLR(i, &master); // remove from master set
                    } else {
/*
                    {{{{{{{{{{{{{{{{{{{{{{ NOT COMPLETED }}}}}}}}}}}}}}}}}
                    {{{{HERE I SHOULD COMPARE THE CLIENT MESSAGE PASSOWRD              IF IT'S THE SAME }}}}}}}}}}    */
                    }
                } // it's SO UGLY!
            }
        }
    }
    
    return 0;
}