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udp(n) Tcl UDP extension udp(n)
See the file man.macros.
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
command 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 specifying 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
system 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
support 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)