NAME¶

udp - Create UDP sockets in Tcl

SYNOPSIS¶

package require Tcl 8.2

package require udp 1.0.11

udp_open ?port? ?reuse? ?ipv6?

udp_conf sock host port

udp_conf sock ?-myport? ?-remote? ?-peer? ?-broadcast bool? ?-ttl count? ?-mcastadd "groupaddr ?netwif?"? ?-mcastdrop "groupaddr ?netwif?"? ?-mcastgroups? ?-mcastloop bool?

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? ?reuse? ?ipv6?

udp_open will open a UDP socket. If a 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.

The following keywords can be used to specify options on the opened socket.

udp_conf sock host port

Deprecated in favour of the standard Tcl fconfigure command.

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? ?-mcastadd "groupaddr ?netwif?"? ?-mcastdrop "groupaddr ?netwif?"? ?-mcastgroups? ?-mcastloop bool?

Deprecated in favour of the standard Tcl fconfigure command.

In addition to being used to configure the remote host, the udp_conf command is used to obtain information about the UDP socket. NOTE all these options are now available using the standard Tcl fconfigure command.

udp_peek sock ?buffersize?

Examine a packet without removing it from the buffer. Option buffersize specifies the maximum buffer size. Value must be between 0 and 16.

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.

Support for IPv6 and allowing a multicast join on a specific network interface is added by Huub Eikens.

SEE ALSO¶

socket(3tcl)

KEYWORDS¶

networking, socket, udp

COPYRIGHT¶

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