socket program help

This is a discussion on socket program help within the Networking/Device Communication forums, part of the General Programming Boards category; Hi, I'm writing a client-server socket program. the client will be an instance of the well-known telnet application. i want ...

  1. #1
    Registered User
    Join Date
    Apr 2007
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    3

    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;
    }

  2. #2
    and the hat of wrongness Salem's Avatar
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    I would suggest you read the forum rules and stop spamming the board
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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