TCP echo demo

[netcomm.h]

 

#ifndef NETCOMM_H
#define NETCOMM_H

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>

#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define MAXLINE 1000
#define LISTENQN 6
#define SERPORT 2400

static void str_echo(int connfd);

/*
 * Read n bytes from a descriptor
 */
ssize_t
readn(int fd, void *vptr, size_t n)
{
    size_t nread;
    size_t nleft;
    char   *ptr;

    nread = 0;
    nleft = n;
    ptr = vptr;

    while (nleft > 0)
    {
        if ( (nread = read(fd, ptr, nleft)) < 0)
        {
            if (errno == EINTR) /* Read again */
                nread = 0;
            else
                return -1;
        }
        else if (nread == 0) /* EOF */
            break;

        nleft -= nread;
        ptr   += nread;
    }

    return (n - nleft);
}

/*
 * Write n bytes into a descriptor
 */
ssize_t
writen(int fd, void *vptr, size_t n)
{
    size_t nleft;
    size_t nwriten;
    void   *ptr;

    nleft   = n;
    nwriten = 0;
    ptr     = vptr;

    while (nleft > 0)
    {
        if ( (nwriten = write(fd, ptr, nleft)) <= 0)
        {
            if (nwriten < 0 && errno == EINTR)
                nwriten = 0;
            else
                return (-1);
        }

        nleft -= nwriten;
        ptr   += nwriten;
    }

    return (n);
}

/*
 * Read a line from descriptor
 */
ssize_t
readline(int fd, void *vptr, size_t maxlen)
{
    int  n, rc;
    char *ptr;
    char c;

    ptr = vptr;

    for (n = 1; n <= maxlen; ++n)
    {
        again:
        if ( (rc = read(fd, &c, 1)) == 1)
        {
            *ptr++ = c;
            if (c == '\n')
                break;
        } else if (rc == 0) /* EOF */
        {
            *ptr = 0;
            return (n - 1);
        } else
        {
            if (errno == EINTR)
               goto again;
            return (-1);
        }
    }

    *ptr = 0;
    return n;
}
#endif



[echo_server.c]

/*
 * Echo server demo
 */
#include "netcomm.h"

int
main(int argc, char **argv)
{
    int                listenfd, clifd;
    struct sockaddr_in cliaddr, serveraddr;
    pid_t              pid;
    socklen_t          cliaddrlen;

    /* Initialize server addr */
    if ( (listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        printf("Create socket error!\n");
        exit(-1);
    }

    bzero(&serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
    serveraddr.sin_port = htons(SERPORT);

    /* Bind server addr to listen fd */
    if (bind(listenfd, &serveraddr, sizeof(serveraddr)) < 0){
        printf("bind addr error!\n");
        exit(-1);
    }

    if (listen(listenfd, LISTENQN) < 0) {
        printf("Listen error!\n");
        exit(-1);
    }

    for (; ;) {
        cliaddrlen = sizeof (cliaddr);
        if ( (clifd = accept(listenfd, &cliaddr, &cliaddrlen)) < 0) {
            if (errno == EINTR)
                continue;
            else
                exit(-1);
        } else {
            if ( (pid = fork()) == 0) {
                close(listenfd);
                str_echo(clifd);
                exit(0);
            }
        }
        close(clifd);
    }

    waitpid(pid, NULL, 0);
}


static void
str_echo(int connfd) {
    size_t n;
    char   buf[MAXLINE];

    again:
    while ( (n = read(connfd, buf, sizeof(buf))) > 0) {
        if (writen(connfd, buf, n) < 0) {
            printf("Write connfd error!\n");
            exit(-1);
        }
    }

    if ( n < 0 && errno == EINTR)
        goto again;
    else if ( n < 0)
        exit(-1);

    exit(0);
}

 

 

[echo_client.c]

 

/*
 * Echo client demo
 */
#include "netcomm.h"

static void str_client(FILE *fp, int connfd);

int
main(int argc, char **argv)
{
    int                clifd;
    struct sockaddr_in serveraddr;

    if (argc != 2) {
        printf("Usage:echo_client <IP>\n");
        exit(-1);
    }

    /* Initialize client fd */
    if ( (clifd = socket(AF_INET, SOCK_STREAM, 0)) < 0){
        printf("Create socket error!\n");
        exit(-1);
    }

    bzero(&serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    if (inet_pton(AF_INET, argv[1], &serveraddr.sin_addr) < 0) {
        printf("inet_pton error!\n");
        exit(-1);
    }
    serveraddr.sin_port = htons(SERPORT);

    if (connect(clifd, &serveraddr, sizeof(serveraddr)) < 0) {
        printf("connect error!\n");
        exit(-1);
    }

    str_client(stdin, clifd);

    exit(0);
}

 

static void
str_client(FILE *fp, int connfd) {
    char   send[MAXLINE], receive[MAXLINE];

    while ( fgets(send, MAXLINE, fp) != NULL) {
        if (writen(connfd, send, sizeof(send)) < 0) {
            printf("writen error!\n");
            exit(-1);
        }

        if (readline(connfd, receive, MAXLINE) == 0) {
            printf("str_client: server terminated.\n");
            return;
        }

        fputs(receive, stdout);
    }

    exit(0);
}