From Computer Networking and Applications, Douglas Comer, Chapter 3

“To demonstrate network programming, we have devised a straightforward API for network communication.”

Comer’s API is an abstraction that simplifies the so-called socket programming API. (The socket API is the standard method applications use to enable themselves to use an IP network.)

/* echoserver.c */

#include <stdlib.h>

#include <stdio.h>

#include <cnaiapi.h>

#define BUFFSIZE 256

/*-----------------------------------------------------------------------

*

* Program: echoserver

* Purpose: wait for a connection from an echoclient and echo data

* Usage: echoserver <appnum>

*

*-----------------------------------------------------------------------

*/

int

main(int argc, char *argv[])

{

connection conn;

int len;

char buff[BUFFSIZE];

if (argc != 2) {

(void) fprintf(stderr, "usage: %s <appnum>\n", argv[0]);

exit(1);

}

/* wait for a connection from an echo client */

conn = await_contact((appnum) atoi(argv[1]));

if (conn < 0)

exit(1);

/* iterate, echoing all data received until end of file */

while((len = recv(conn, buff, BUFFSIZE, 0)) > 0)

(void) send(conn, buff, len, 0);

send_eof(conn);

return 0;

}