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Message-ID: <F5AFD56E32E8D21191090060974838B1018D67B2@ulm003.vs.dasa.de>
From: "Lasslop, Andre" <Andre DOT Lasslop AT vs DOT dasa DOT de>
To: "'cygwin AT cygwin DOT com'" <cygwin AT cygwin DOT com>
Subject: socket-write does not immediatly output
Date: Thu, 1 Mar 2001 11:17:06 +0100 
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Hello,
trying to write to a socket-connection between a simple C-program and a
TCL-script, I got a problem. The output does not immediatly occur at the
reading end, but after stop the connection. Also explicite fflush() does not
help. Here is the code for both programs (The C-Code is the example from the
GNU-C-Library-Documentation). Any suggestions ? Thanks.

André Lasslop
> E-mail:    mailto:andre DOT lasslop AT vs DOT dasa DOT de
> 
> 
> 
################################## The C-Client-Program
#########################################################

/*
 * Test of socket open, close and data transmission.
 */

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#include <fcntl.h>

#define PORT       5555
#define MESSAGE    "Yow!!! Are we having fun yet?!?"
#define SERVERHOST "lasan"

void
init_sockaddr(
    struct sockaddr_in *name,
    const char *hostname,
    unsigned short int port )
{
    struct hostent *hostinfo;

    name->sin_family = AF_INET;
    name->sin_port = htons( port );
    hostinfo = gethostbyname( hostname );
    if ( hostinfo == NULL ) {
	fprintf( stderr, "Unknown host %s,\n", hostname );
	exit( EXIT_FAILURE );	
    }
    name->sin_addr = *(struct in_addr *) hostinfo->h_addr;
}

void
/*  write_to_server(int filedes) */
write_to_server(FILE * pfd)
{
    int nbytes;

    printf("writing data\n");
    nbytes = write( fileno(pfd), MESSAGE, strlen(MESSAGE) );
    fflush(pfd);
/*      nbytes = write( filedes, MESSAGE, strlen(MESSAGE) ); */
    if ( nbytes < 0 ) {
	perror( "write_to_server" );
	exit( EXIT_FAILURE );
    }
}

int
main( void )
{
    extern void init_sockaddr(struct sockaddr_in *name,
			      const char *hostname,
			      unsigned short int port);

    int i;
    int sock;
    struct sockaddr_in servername;
    char hostname[0xff];
    FILE * pfd;
    
    gethostname( hostname, 0xff );
    printf( "Max. Hostname-Length : %d\n", MAXHOSTNAMELEN );
    printf( "Hostname : >%s<\n", hostname );
    
    /* Create the socket */

    sock = socket( PF_INET, SOCK_STREAM, 0);
    if ( sock < 0 ) {
	perror( "create socket (client)" );
	exit( EXIT_FAILURE );	
    }

    /* Create a stream-id */

    pfd = fdopen( sock, "w");
    
    /* Connect to the server. */

    init_sockaddr( &servername, SERVERHOST, PORT );
    if ( 0 > connect( sock,
		      (struct sockaddr *) &servername,
		      sizeof(servername) )) {
	perror( "connect socket (client)" );
	exit( EXIT_FAILURE );	
    }

    /* Send data to the server */

    for ( i=5 ; i ; i--) {
	write_to_server( pfd );
/*  	write_to_server( sock ); */
	sleep(1);
    }
    
    close( sock );
    
    exit( EXIT_SUCCESS );
}

######################################### The TCL-Server-Script
####################################

#!/bin/sh
# the next line restarts using tclsh\
exec cygtclsh80 "$0" "$@"

global eth
set eth(debug) 1

proc svc { chan } {
    global eth
    
    if [eof $chan] {
	if $eth(debug) { puts "Closing Channel" }
	close $chan
	set eth(stop) $chan
    } else {
	binary scan [read $chan] c* temp
	puts "Channel : $temp"
	flush stdout
    }
}

proc acc { chan addr port } {
    global eth
    
    if $eth(debug) { puts "Opening Channel" }

    fconfigure $chan -translation binary
    fileevent $chan readable [list svc $chan]
}

set sockid [socket -server acc 5555]

vwait eth(stop)

close $sockid

exit

#################################### End of Code
#####################################








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