udp(n)								 Tcl UDP extension							    udp(n)

__________________________________________________________________________________________________________________________________________________

NAME

       udp - Create UDP sockets in Tcl

SYNOPSIS

       package require Tcl  8.2

       package require udp  1.0

       udp_open ?port?

       udp_conf sock host port

       udp_conf sock ?-myport? ?-remote? ?-peer? ?-broadcast bool? ?-ttl count?

       udp_conf ?-mcastadd groupaddr?

       udp_conf ?-mcastdrop groupaddr?

       udp_peek sock ?buffersize?

_________________________________________________________________

DESCRIPTION

       This  package  provides support for using UDP through Tcl. The package provides a new channel type and attempts to permit the use of packet
       oriented UDP over stream oriented Tcl channels. The package defined three commands but udp_conf should be considered depreciated in  favour
       of the standard Tcl command fconfigure.

COMMANDS

       udp_open ?port?
	      udp_open will open a UDP socket. If port is specified the UDP socket will be opened on that port. Otherwise the system will choose a
	      port and the user can use the udp_conf command to obtain the port number if required.

       udp_conf sock host port
	      udp_conf in this configuration is used to specify the remote destination for packets written to this sock. You must call	this  com-
	      mand before writing data to the UDP socket.

       udp_conf sock ?-myport? ?-remote? ?-peer? ?-broadcast bool? ?-ttl count?
	      In addition to being used to configure the remote host, the udp_conf command is used to obtain information about the UDP socket.

	      -myport
		     Returns the local port number of the socket.

	      -remote
		     Returns the remote hostname and port number as set using udp_conf sock host port.

	      -peer  Returns the remote hostname and port number for the packet most recently received by this socket.

	      -broadcast ?boolean?
		     UDP packets can listen and send on the broadcast address. For some systems a flag must be set on the socket to use broadcast.
		     With no argument this option will return the broadcast setting. With a boolean argument the setting can be modified.

	      -ttl ?count?
		     The time-to-live is given as the number of router hops the packet may do. For multicast packets this is important in specify-
		     ing  the distribution of the packet. The system default for multicast is 1 which restricts the packet to the local subnet. To
		     permit packets to pass routers, you must increase the ttl. A value of 31 should keep it within a site, while 255 is global.

       udp_conf ?-mcastadd groupaddr?

       udp_conf ?-mcastdrop groupaddr?
	      tcludp sockets can support IPv4 multicast operations. To recieve multicast packets the application has to notify the operating  sys-
	      tem that it should join a particular multicast group. These are specified as addresses in the range 224.0.0.0 to 239.255.255.255.

       udp_peek sock ?buffersize?
	      Examine a packet without removing it from the buffer.  This function is not available on windows.

EXAMPLES

       # Send data to a remote UDP socket
       proc udp_puts {host port} {
	   set s [udp_open]
	   fconfigure $s -remote [list $host $port]
	   puts $s "Hello, World"
	   close $f
       }

       # A simple UDP server
       package require udp

       proc udpEventHandler {sock} {
	   set pkt [read $sock]
	   set peer [fconfigure $sock -peer]
	   puts "$peer: [string length $pkt] {$pkt}"
	   return
       }

       proc udp_listen {port} {
	   set srv [udp_open $port]
	   fconfigure $srv -buffering none -translation binary
	   fileevent $srv readable [list ::udpEventHandler $srv]
	   puts "Listening on udp port: [fconfigure $srv -myport]"
	   return $srv
       }

       set sock [udp_listen 53530]
       vwait forever
       close $sock

       # A multicast demo.
       proc udpEvent {chan} {
	   set data [read $chan]
	   set peer [fconfigure $chan -peer]
	   puts "$peer [string length $data] '$data'"
	   if {[string match "QUIT*" $data]} {
	       close $chan
	       set ::forever 1
	   }
	   return
       }

       set group 224.5.1.21
       set port  7771
       set s [udp_open $port]
       fconfigure $s -buffering none -blocking 0
       fconfigure $s -mcastadd $group -remote [list $group $port]
       fileevent $s readable [list udpEvent $s]
       puts -nonewline $s "hello, world"
       set ::forever 0
       vwait ::forever
       exit

HISTORY

       Some	 of	 the	  code	    in	    this     extension	   is	  copied     from     Michael	  Miller's     tcludp	  package.
       (http://www.neosoft.com/tcl/ftparchive/sorted/comm/tcludp-1.0/) Compared with Michael's UDP extension, this extension provides Windows sup-
       port and provides the ability of using 'gets/puts' to read/write the socket. In addition, it provides more configuration ability.

       Enhancements to support binary data and to setup the package for the Tcl Extension Architecture by Pat Thoyts.

SEE ALSO

       socket(n)

KEYWORDS

       networking, socket, udp

COPYRIGHT

       Copyright (c) 1999-2000 Columbia University; all rights reserved

udp								       1.0.7								    udp(n)