$ cat mysrc/u_inetd.c 
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <signal.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#define P_EEXIT fprintf(stderr,"Abnormal exit at %s:%d\n",__FILE__,__LINE__),exit(1)
int main( int argc, char **argv ){
        int i, s, ns, loa, t_on = 1, ka = 10, only1 = 0, maxbuf=65535 ;
        union {
                struct sockaddr sa ;
                struct sockaddr_in sin ;
        } u ;
        struct sigaction siga ;
        u.sin.sin_port = 0 ;
        u.sin.sin_addr.s_addr = INADDR_ANY ;
        for ( i = 1 ; i < argc ; i++ ){
                if ( !strcmp( argv[i], "-l" )){
                        u.sin.sin_addr.s_addr = INADDR_LOOPBACK ;
                } else if ( !strcmp( argv[i], "-o" )){
                        only1 = 1 ;
                } else if ( u.sin.sin_port == 0 ){
                        if ( 1 > atoi( argv[i] )){
                                break ;
                        }
                        u.sin.sin_port = atoi( argv[i] );
                }
                else    /* must be command */
                        break ;
        }
        if ( u.sin.sin_port == 0
          || i == argc ){
                printf(
"Usage:  %s [ -l ] [ -o ] <port> <cmd> [<cmd args>]\n"
"\n"
"Listens on port for tcp connections, and for every connection,\n"
" runs <cmd> with any <cmd args>\n"
"  and with the socket as stdin and stdout (but stderr is preserved)\n"
"   under the user's id.  (Be careful!)\n"
"\n"
"The -l option restricts connections to clients on the same host\n"
" for greater security.\n"
"The -o option restricts the server to only one (1) service at a time\n"
" for commands that need exclusive control of a resource,\n"
" by waiting for child termination.  This can result in a hung server.\n"
"The <cmd> must be exec() compatible, so if it is not a sh shell script,\n"
" make sure to have '#!<full_path_of_interpreter> [ <one_arg> ]' as line 1.\n"
"\n",
                        argv[0] );
                exit( 1 );
        }
        /* ensure that no fd's are open that are not needed,
                as sh does not allow >&##       */
        for ( s = 0 ; s < 128 ; s++ ){
                if ( s != 2 )
                        close( s );
        }
        if ( 0 > ( s = socket( PF_INET, SOCK_STREAM, NULL ))){
                perror( "socket( PF_INET, SOCK_STREAM, NULL )" );
                P_EEXIT ;
        }
        u.sin.sin_family = AF_INET ;
        if ( setsockopt(  s, IPPROTO_TCP, TCP_NODELAY, (char *)&t_on, sizeof(int))){
                 perror( "setsockopt( s, IPPROTO_TCP, TCP_NODELAY, (char *)&t_on, sizeof(int))" );
                P_EEXIT ;
        }
        if ( setsockopt( s, SOL_SOCKET, SO_REUSEADDR, (char*)&t_on,
                sizeof(int))){
                perror( "setsockopt( s, SOL_SOCKET, SO_REUSEADDR, (char*)&t_on, sizeof(int) )" );
                P_EEXIT ;
        }
        if ( setsockopt( s, SOL_SOCKET, SO_KEEPALIVE, (char*)&ka,
                sizeof(int))){
                perror( "setsockopt( s, SOL_SOCKET, SO_KEEPALIVE, (char*)&ka, sizeof(int) )" );
                P_EEXIT ;
        }
        if ( setsockopt(  s, SOL_SOCKET, SO_RCVBUF, (char *)&maxbuf, sizeof(int))){
                 perror( "setsockopt( s, IPPROTO_TCP, SO_RCVBUF, (char *)&maxbuf, sizeof(int))" );
                P_EEXIT ;
        }
        if ( setsockopt(  s, SOL_SOCKET, SO_SNDBUF, (char *)&maxbuf, sizeof(int))){
                 perror( "setsockopt( s, IPPROTO_TCP, SO_SNDBUF, (char *)&maxbuf, sizeof(int))" );
                P_EEXIT ;
        }
        if ( bind( s, &u.sa, sizeof(u.sa))){
                perror( "bind()" );
                P_EEXIT ;
        }
        if ( listen( s, 256 )){
                perror( "listen( s, 256 )" );
                P_EEXIT ;
        }
        siga.sa_handler = NULL ;
        sigemptyset( &siga.sa_mask );
        siga.sa_flags = SA_NOCLDWAIT ;
        sigaction( SIGCHLD, &siga, NULL );
next:
        loa = sizeof(u.sa);
        if ( 0 > ( ns = accept( s, &u.sa, &loa ))){
                if ( errno == EINTR
                  || errno == EAGAIN ){
                        goto next ;
                }
                perror( "accept( s, &u.sa, sizeof(u.sa) )" );
                P_EEXIT ;
        }
refork:
        switch ( fork()){
        case -1 :
                sleep( 1 );
                goto refork ;
        case 0 :
                break ;
        default:                /* Parent */
                close( ns );
                if ( only1 ){
                        do {
                                wait( NULL );
                        } while ( errno != ECHILD );
                }
                goto next ;
        }
        /* child */
        close(s);
        do {
                s = dup(ns);
        } while ( s < 1 && s >= 0 );
        if ( ns > 2 ){
                close(ns);
        }
        execvp( argv[i], argv + i );
        /* should never get here */
        perror( "execvp( argv[i], argv + i )" );
        P_EEXIT ;
}