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

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define    QLEN           5    /* maximum connection queue length    */#define    BUFSIZE        4096

externint    errno;

void    reaper(int);
int    TCPechod(int fd);
int    errexit(constchar *format, ...);
int    passiveTCP(constchar *service, int qlen);

/*------------------------------------------------------------------------ * main - Concurrent TCP server for ECHO service *------------------------------------------------------------------------ */int
main(int argc, char *argv[])
{
    char    *service = "echo";    /* service name or port number    */struct    sockaddr_in fsin;    /* the address of a client    */int    alen;            /* length of client's address    */int    msock;            /* master server socket        */int    ssock;            /* slave server socket        */switch (argc) {
    case    1:
        break;
    case    2:
        service = argv[1];
        break;
    default:
        errexit("usage: TCPechod [port]\n");
    }

    msock = passiveTCP(service, QLEN);

    (void) signal(SIGCHLD, reaper);

    while (1) {
        alen = sizeof(fsin);
        ssock = accept(msock, (struct sockaddr *)&fsin, &alen);
        if (ssock < 0) {
            if (errno == EINTR)
                continue;
            errexit("accept: %s\n", strerror(errno));
        }
        switch (fork()) {
        case 0:        /* child */
            (void) close(msock);
            exit(TCPechod(ssock));
        default:    /* parent */
            (void) close(ssock);
            break;
        case -1:
            errexit("fork: %s\n", strerror(errno));
        }
    }
}

/*------------------------------------------------------------------------ * TCPechod - echo data until end of file *------------------------------------------------------------------------ */int
TCPechod(int fd)
{
    char    buf[BUFSIZ];
    int    cc;

    while (cc = read(fd, buf, sizeof buf)) {
        if (cc < 0)
            errexit("echo read: %s\n", strerror(errno));
        if (write(fd, buf, cc) < 0)
            errexit("echo write: %s\n", strerror(errno));
    }
    return 0;
}

/*------------------------------------------------------------------------ * reaper - clean up zombie children *------------------------------------------------------------------------ *//*ARGSUSED*/void
reaper(int sig)
{
    int    status;

    while (wait3(&status, WNOHANG, (struct rusage *)0) >= 0)
        /* empty */;
}