The Tcl core has supported TCP sockets with the socket command since version 7 or so but UDP must be supplied by an extension (but see "UDP in the Tcl core"). The following extensions provide UDP support:
The TclUDP package is quite simple to use. It has only two commands to create and configure udp sockets. There is no 'recv' or 'send', rather, you read from a TclUDP socket with 'read' and write to it using 'puts'.
The TclUDP package supports UDP sockets on Windows and Unix with fileevent handling and has recently been enhanced to support the TEA2 build system and to enable the transmission of binary data. It is now a project at sourceforge [L1 ] and the lastest releases will be available at [L2 ]
Also http://students.cs.tamu.edu/mmiller/tcl/channel.html which is the original base for tcludp.
PT 2003-06-13: This is a simple demo server that I use in testing:
package require udp
proc udpEventHandler sock {
set pkt [read $sock]
set peer [udp_conf $sock -peer]
puts "$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: [udp_conf $srv -myport]"
return $srv
}
if {$tcl_interactive} {
puts "call udp_listen portnum to begin"
} else {
eval [list udp_listen] $argv
vwait forever
}And a corresponding server socket can be obtained using:
proc udp_create {host port} {
set s [udp_open]
udp_conf $s $host $port
fconfigure $s -buffering none -translation binary
return $s
}then use
set sock [udp_create $server $portnum];# eg localhost 9876 puts -nonewline $sock "MyData - including binary \0\1\2\3"
Mike Tuxford 2003-01-30: It was mentioned in c.l.t that there aren't many examples of tcludp usage around so I'll add this simple one that listens on port 1434 which is the MSSQL port and has been in the news a lot lately due to major exploits.
package require udp
proc udpEventHandler {} {
global fd
puts "event triggered..."
puts "Data: [gets $fd(udp)]"
puts "Peer: [udp_conf $fd(udp) -peer]"
return
}
set fd(udp) [udp_open 1434]
fileevent $fd(udp) readable udpEventHandler
puts "Listening on udp port: [udp_conf $fd(udp) -myport]"
vwait __forever__shedi 2003-12-10: Wake On Lan Example (the magic packet). Usage: WakeOnLan 10.255.255.255 000783104R83
package require udp
proc WakeOnLan {broadcastAddr macAddr} {
set net [binary format H* [join [split $macAddr -:] {}]]
set pkt [binary format c* {0xff 0xff 0xff 0xff 0xff 0xff}]
for {set i 0} {$i < 16} {incr i} {
append pkt $net
}
# Open UDP and Send the Magic Paket.
set udpSock [udp_open];
udp_conf $udpSock $broadcastAddr 4580;
fconfigure $udpSock -translation binary;
puts $udpSock $pkt
flush $udpSock;
close $udpSock
}sbron: In my experiments this works on windows, but not on linux. On linux the code has to specifically allow broadcasting using something like the following at an appropriate spot in the c code:
int yes = 1; setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &yes, sizeof(int));
PT 2004-11-19: The in-development version 2.x tcludp supports setting the broadcast option on the socket. If you want to try it out, checkout the dev-2 branch from the tcludp sourceforge CVS.
2006-06-06: There is no dev-2 branch at tcludp.sourceforge.net (anymore?), can someone provide a link where to get tcludp 2.x ?
Here is a sample of a simplistic chat using broadcast UDP packets using the tcludp 2.0.0 api.
# udpmsg.tcl - Copyright (C) 2004 Pat Thoyts <[email protected]> # # Demo chat application. # # This uses broadcast UDP packets to send chat messages to the network. # # $Id: 16733,v 1.2 2006-09-14 06:01:04 jcw Exp $ package require Tk 8.4 package require udp 2 variable Port 7531 variable Network 172.16.255.255 variable server variable client # handle incoming packets on the udp server socket. proc udpEventHandler {sock} { set pkt [read $sock] set peer [fconfigure $sock -peer] AddMessage "$peer $pkt" return } # create a udp server socket proc udp_listen {port} { set srv [udp] fconfigure $srv \ -sockname [list {} $port] \ -blocking 0 \ -buffering none \ -translation binary \ -broadcast 1 \ -reuseaddr 1 fileevent $srv readable [list ::udpEventHandler $srv] AddMessage "Listening on udp port: [fconfigure $srv -sockname]" return $srv } # create a udp client socket proc udp_create {host port} { set s [udp] fconfigure $s -remote [list $host $port] fconfigure $s -buffering none -translation binary return $s } proc CreateGui {} { text .t -yscrollcommand {.s set} scrollbar .s -command {.t yview} entry .e -textvariable ::msg button .ok -text Send -underline 0 -command {SendMessage $::msg} button .ex -text Exit -underline 1 -command {destroy .} grid .t - .s -sticky news grid .e .ok .ex -sticky ew grid columnconfigure . 0 -weight 1 grid rowconfigure . 0 -weight 1 bind .e <Return> {.ok invoke} } proc SendMessage {msg} { variable client puts $client $msg } proc AddMessage {msg} { if {[string length $msg] > 0} { .t insert end $msg } } if {!$tcl_interactive} { CreateGui set server [udp_listen $Port] set client [udp_create $Network $Port] tkwait window . close $server close $client exit 0 }
UDP enabled packages
PT: In tcllib - the dns package is capable of using udp if available. Also the time and ntp packages.
Further note Trivial FTP.