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Gift server demonstration
Standard Libraries and other headers example from a Well House Consultants training course
More on Standard Libraries and other headers [link]

This example is described in the following article(s):
   • Sockets, time handling and keyboard interrupt handling in C - [link]

This example references the following resources:
http://en.wikibooks.org/wiki/C_Programming/Networking_in_UNIX

Source code: g2.c Module: C211
/* Originally based on an original from
        http://en.wikibooks.org/wiki/C_Programming/Networking_in_UNIX
available under creative commons license.

Gift server demonstration

*/


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

#include <signal.h>
#include <time.h>

#define PORTNUM 13579

int hitter = 0; /* Yuk - global! - done for the signal handler*/
int mysocket = 0 ; /* ditto! */
int consocket = 0 ; /* ditto! */

/* Signal handler - run this if ^C is entered on server */

void cc(int sig) {
        signal(sig, SIG_IGN); /* Not sure why we briefly ignore! */
        printf("Can't kill me this way ;-) (but if you persist, perhaps ...)\n");
        hitter++;
        if (hitter > 5) {
                /* ALSO need to make sure we've read anything buffered before close? */
                printf("Persistant, aren't you!\n");
                if (mysocket) close(mysocket);
                if (consocket) close(consocket);
                exit(EXIT_SUCCESS);
                }
        signal(SIGINT, cc); /* re-enable ^C trap to here again if needed */
        }

int main(int argc, char *argv[])
{
    int ncr ; /* number chars read */

    FILE *logfile;

    char *greeting = "Please enter your gift: ";
    char *youget = "In return you receive: ";

    char giftstore[257] = "Two pints of lager and a packet of pork scratchings\n";
    char giftbox[257];

    struct sockaddr_in dest; /* socket info about the machine connecting to us */
    struct sockaddr_in serv; /* socket info about our server */
    socklen_t socksize = sizeof(struct sockaddr_in);

    signal(SIGINT, cc); /* Handler for ^C on the server */

    memset(&serv, 0, sizeof(serv)); /* zero the struct before filling the fields */
    serv.sin_family = AF_INET; /* set the type of connection to TCP/IP */
    serv.sin_addr.s_addr = htonl(INADDR_ANY); /* set our address to any interface */
    serv.sin_port = htons(PORTNUM); /* set the server port number */

        /* create a socket, bind to it, listen (up to 5 Q'd request) and accept */

    mysocket = socket(AF_INET, SOCK_STREAM, 0);
    bind(mysocket, (struct sockaddr *)&serv, sizeof(struct sockaddr));
    listen(mysocket, 5);
    consocket = accept(mysocket, (struct sockaddr *)&dest, &socksize);

    while(consocket) {
        logfile = fopen("logmehere.txt","a");

                /* log who connected and when (two alternatives in this demo) */

        time_t now;
        now = time(NULL);
        fprintf(logfile,"%s- Incoming connection from %s\n",
                                ctime(&now), inet_ntoa(dest.sin_addr));

        struct timeval details;
        gettimeofday(&details);
        fprintf(logfile,"%s- Incoming connection from %s\n",
                                ctime(&(details.tv_sec)), inet_ntoa(dest.sin_addr));

                /* protocol exchange with client */

        send(consocket, greeting, strlen(greeting), 0);

        ncr = read(consocket, giftbox, sizeof(giftbox)-1);
        giftbox[ncr] = '\0';

        send(consocket, youget, strlen(youget), 0);
        send(consocket, giftstore, strlen(giftstore), 0);

                /* server closes connection when it has sent */

        close(consocket);

                /* complete logging to file */

        fprintf(logfile,"-sent: %s-received: %s\n",giftstore,giftbox);
        fclose(logfile);

                /* Save the new gift into the giftstore */

        strcpy(giftstore,giftbox);

                /* Await next connection */

        consocket = accept(mysocket, (struct sockaddr *)&dest, &socksize);
    }

    close(mysocket);
    return EXIT_SUCCESS;
}

/* Sample output - server

trainee@kingston:~/cmar15$ make g2
cc g2.c -o g2
trainee@kingston:~/cmar15$ ./g2
^CCan't kill me this way ;-) (but if you persist, perhaps ...)
^CCan't kill me this way ;-) (but if you persist, perhaps ...)
^CCan't kill me this way ;-) (but if you persist, perhaps ...)
^CCan't kill me this way ;-) (but if you persist, perhaps ...)
^CCan't kill me this way ;-) (but if you persist, perhaps ...)
^CCan't kill me this way ;-) (but if you persist, perhaps ...)
Persistant, aren't you!
trainee@kingston:~/cmar15$

----------------------------------------------------------------------------------

Sample output - a client

trainee@kingston:~/cmar15$ telnet localhost 13579
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Please enter your gift: Sticky Toffee Pudding
In return you receive: Two pints of lager and a packet of pork scratchings
Connection closed by foreign host.
trainee@kingston:~/cmar15$ telnet localhost 13579
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Please enter your gift: Pea Pie
In return you receive: Sticky Toffee Pudding
Connection closed by foreign host.
trainee@kingston:~/cmar15$

Sample log file

Fri Mar 27 12:26:42 2015
- Incoming connection from 192.168.200.37
Fri Mar 27 12:26:42 2015
- Incoming connection from 192.168.200.37
-sent: Feet
-received: hands

Sat Mar 28 07:06:16 2015
- Incoming connection from 127.0.0.1
Sat Mar 28 07:06:16 2015
- Incoming connection from 127.0.0.1
-sent: Two pints of lager and a packet of pork scratchings
-received: Sticky Toffee Pudding

Sat Mar 28 07:07:06 2015
- Incoming connection from 127.0.0.1
Sat Mar 28 07:07:06 2015
- Incoming connection from 127.0.0.1
-sent: Sticky Toffee Pudding
-received: Pea Pie

*/


Learn about this subject
This module and example are covered on the following public courses:
 * Learning to Program in C
 * Learning to program in C and C++
 * Programming in C
 * C and C++ Programming
 * Learning to program in C and C++
 * C and C++ Programming
Also available on on site courses for larger groups

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Other Examples
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