_HIPPI AND HIGH-PERFORMANCE LANS_
by Andy Nicholson

[LISTING ONE]
 
/* echo.h - header file for the echo example programs */

#define BUFSIZE         512
#define ECHOPORT        7500

#define ECHO_REQUEST    1
#define ECHO_REPLY      2


[LISTING TWO]
 
/* echos.c  --  The echo service server program  */

#include <errno.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#include "echo.h"

main()
{
        char buf[BUFSIZE];
        int s, c;
        struct sockaddr_in sin, peer;
        int peerlen;
        int mlen;

        /* get a socket */
        if ((s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1) {
                perror("can't open socket");
                exit(1);
        }
        /* bind to local address and echo port */
        bzero(&sin, sizeof(sin));
        sin.sin_family = AF_INET;
        sin.sin_port = ECHOPORT;
        if (bind(s, &sin, sizeof(sin)) == -1) {
                perror("cannot bind");
                close(s);
                exit(1);
        }
        /* start listening for connections */
        if (listen(s, 5) == -1) {
                perror("cannot listen");
                close(s);
                exit(1);
        }
        /* accept and process incoming messages */
        while (1) {
                if ((c = accept(s, &peer, &peerlen)) == -1) {
                        perror("cannot accept");
                        close(s);
                        exit(1);
                }
                /* simple processing, read message, echo it back */
                if ((mlen = read(c, buf, BUFSIZE)) == -1) {
                        perror("read error");
                        close(c);
                        continue;
                }
                if (write(c, buf, mlen) != mlen) {
                        perror("write error");
                        close(c);

                        continue;
                }
                printf("%d byte message received and echoed\n", mlen);
                close(c);
        }
}  /* end of main */



[LISTING THREE]
 
/* echoc.c -- The echo service client program  */

#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#include "echo.h"

main(argc, argv)
int argc;
char **argv;
{
        char buf[BUFSIZE];
        int s;
        struct sockaddr_in sin;
 
        if (argc < 2) {
                printf("must specify a server in internet dot notation\n");
                exit(1);
        }
        /* get a socket */
        if ((s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1) {
                perror("can't open socket");
                exit(1);
        }

        /* bind to local address and available port */
        bzero(&sin, sizeof(sin));
        sin.sin_family = AF_INET;
        if (bind(s, &sin, sizeof(sin)) == -1) {
                perror("cannot bind");
                close(s);
                exit(1);
        }
        /* connect to echo server at echo port */
        bzero(&sin, sizeof(sin));
        sin.sin_family = AF_INET;
        sin.sin_port = ECHOPORT;
        sin.sin_addr.s_addr = inet_addr(argv[1]);
        if (connect(s, &sin, sizeof(sin)) == -1) {
                perror("cannot connect");
                close(s);
                exit(1);
        }
        /* send a message to be echoed */
        if (write(s, buf, BUFSIZE) != BUFSIZE) {
                perror("write error");
                exit(1);
        }
        /* read the echoed message back */
        if (read(s, buf, BUFSIZE) != BUFSIZE) {
                perror("read error");
                exit(1);
        }
        printf("%d byte message echoed by echo server\n", BUFSIZE);
        close(s);
        exit(0);
}  /* end of main */


[LISTING FOUR]
 
/* echop.c -- The echo service peer program  */

#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h>

#include "echo.h"

main(argc, argv)
int argc;
char **argv;
{
        int s;
        struct sockaddr_in sin;
        int status;

        int width;
        fd_set readfds, writefds, exceptfds;
        struct timeval timeout;
        if (argc < 2) {
                printf("must specify a peer in internet dot notation\n");
                exit(1);
        }
        /* setup passive socket */
        if ((s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1) {
                perror("can't open passive socket");
                exit(1);
        }
        /* bind to local address and echo port */
        bzero(&sin, sizeof(sin));
        sin.sin_family = AF_INET;
        sin.sin_port = ECHOPORT;
        if (bind(s, &sin, sizeof(sin)) == -1) {
                perror("cannot bind");
                close(s);
                exit(1);
        }
        /* start listening for connections */
        if (listen(s, 5) == -1) {
                perror("cannot listen");
                close(s);
                exit(1);
        }
        /* initial select parameters */

        FD_ZERO(&writefds);
        FD_ZERO(&exceptfds);
        width = s+1;  /* only file descriptor we want to check */
        timeout.tv_sec = 0;  /* set timeval for polling */
        timeout.tv_usec = 0;

        while (1) {
                /* check for and process incoming connection requests */
                FD_SET(s, &readfds);
                while ((status = select(width, &readfds, &writefds,
                                     &exceptfds, &timeout)) > 0) {
                        do_respond(s);
                        FD_SET(s, &readfds);
                }
                if (status == -1) {
                        perror("select failed");
                }
                do_request(argv[1]);
        }
}  /* end of main */
int
do_respond(s)
int s;
{
        int c;
        struct sockaddr_in peer;
        int peerlen = sizeof(peer);

        if ((c = accept(s, &peer, &peerlen)) == -1) {
                perror("accept failed");
                return(-1);
        }
        do_echo(c);
        close(c);
        return(0);

}  /* end of do_respond */

int
do_request(dst)
char *dst;
{
        int s;
        struct sockaddr_in sin;
static  pid_t pid = 0;
        int status;
        /* Wait for child if we have already forked. */
        if (pid) {
                wait(&status);
                pid = 0;
        }
        /* get a socket */
        if ((s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1) {
                perror("can't open socket");
                return(-1);
        }
        /* bind to local address and available port */
        bzero(&sin, sizeof(sin));
        sin.sin_family = AF_INET;
        if (bind(s, &sin, sizeof(sin)) == -1) {
                perror("cannot bind");
                return(-1);
        }
        /* connect to echo server at echo port */
        bzero(&sin, sizeof(sin));
        sin.sin_family = AF_INET;
        sin.sin_port = ECHOPORT;
        sin.sin_addr.s_addr = inet_addr(dst);
        if (connect(s, &sin, sizeof(sin)) == -1) {
                perror("connection failed");
                close(s);
                return(-1);
        }
        /* fork process to be form active request */
        if ((pid = fork()) == -1) {
                perror("Cannot fork");
                pid = 0;
                return(-1);
        }
        /* return if parent so we can go back and look for incoming
         * service requests. */
        if (pid > 0) {
                close(s);
                return(0);
        }
        /* child uses echo service */
        do_echo(s);

        close(s);
        exit(0);
}  /* end of do_request */
                        
int
do_echo(s)
int s;
{
        char buf[BUFSIZE];
        int recvlen;
        int sendlen = BUFSIZE;
        /* send a message to be echoed */
        buf[0] = ECHO_REQUEST;
        if (write(s, buf, sendlen) != sendlen) {
                perror("sending: write error");
                exit(1);
        }
        printf("sent echo request\n");
        /* read an incoming message */
        if ((recvlen = read(s, buf, BUFSIZE)) == -1) {
                perror("reading message: read error");
                exit(1);
        }
        /* echo message if it is an echo request */
        if (buf[0] == ECHO_REQUEST) {
                buf[0] = ECHO_REPLY;
                if (write(s, buf, recvlen) != recvlen) {
                        perror("echoing: write error");
                        exit(1);
                }
                printf("received echo request - sent echo reply\n");
        } else {  /* must be reply */
                printf("received echo reply\n");
        }
        /* read another incoming message */
        if ((recvlen = read(s, buf, BUFSIZE)) == -1) {
                perror("reading message: read error");
                exit(1);
        }
        /* echo message if it is an echo request */
        if (buf[0] == ECHO_REQUEST) {
                buf[0] = ECHO_REPLY;
                if (write(s, buf, recvlen) != recvlen) {
                        perror("echoing: write error");
                        exit(1);
                }
                printf("received echo request - sent echo reply\n");
        } else {  /* must be reply */
                printf("received echo reply\n");
        }

        return(0);

}  /* end of do_echo */