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'\" Copyright (c) 1999-2000 Columbia University; all rights reserved
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.TH "udp" 3tcl 1.0.10 udp "Tcl UDP extension"
.BS
.SH NAME
udp \- Create UDP sockets in Tcl
.SH SYNOPSIS
package require \fBTcl  8.2\fR
.sp
package require \fBudp  1.0\fR
.sp
\fBudp_open\fR ?\fIport\fR? ?\fIreuse\fR? ?\fIipv6\fR?
.sp
\fBudp_conf\fR \fIsock\fR \fIhost\fR \fIport\fR
.sp
\fBudp_conf\fR \fIsock\fR \fI?-myport?\fR \fI?-remote?\fR \fI?-peer?\fR \fI?-broadcast bool?\fR \fI?-ttl count?\fR \fI?-mcastadd "groupaddr ?netwif?"?\fR \fI?-mcastdrop "groupaddr ?netwif?"?\fR \fI?-mcastgroups?\fR \fI?-mcastloop bool?\fR
.sp
\fBudp_peek\fR \fIsock\fR ?\fIbuffersize\fR?
.sp
.BE
.SH 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
\fBudp_conf\fR should be considered depreciated in favour of the standard
Tcl command \fBfconfigure\fR.
.SH COMMANDS
.TP
\fBudp_open\fR ?\fIport\fR? ?\fIreuse\fR? ?\fIipv6\fR?
\fBudp_open\fR will open a UDP socket. If \fIport\fR is specified the UDP
socket will be opened on that port. Otherwise the system will choose a port
and the user can use the \fBudp_conf\fR command to obtain the port number
if required.
.sp
The following keywords can be used to specify options on the opened socket.
.RS
.TP
\fIreuse\fR
Using this keyword sets the SO_REUSEADDR socket option which permits multiple sockets to
be bound to the same address/port combination.
.TP
\fIipv6\fR
By default a IPv4 socket is created. When keyword \fIipv6\fR is specified an IPv6
socket is opened.
.RE
.TP
\fBudp_conf\fR \fIsock\fR \fIhost\fR \fIport\fR
\fIDeprecated\fR in favour of the standard Tcl \fBfconfigure\fR command.
.sp
\fBudp_conf\fR in this configuration is used to specify the remote destination
for packets written to this \fIsock\fR. You must call this command before
writing data to the UDP socket.
.TP
\fBudp_conf\fR \fIsock\fR \fI?-myport?\fR \fI?-remote?\fR \fI?-peer?\fR \fI?-broadcast bool?\fR \fI?-ttl count?\fR \fI?-mcastadd "groupaddr ?netwif?"?\fR \fI?-mcastdrop "groupaddr ?netwif?"?\fR \fI?-mcastgroups?\fR \fI?-mcastloop bool?\fR
\fIDeprecated\fR in favour of the standard Tcl \fBfconfigure\fR command.
.sp
In addition to being used to configure the remote host, the \fBudp_conf\fR
command is used to obtain information about the UDP socket. NOTE all these options
are now available using the standard Tcl \fBfconfigure\fR command.
.RS
.TP
\fI-myport\fR
Returns the local port number of the socket.
.TP
\fI-remote\fR
Returns the remote hostname and port number as set using
\fBudp_conf\fR \fIsock\fR \fIhost\fR \fIport\fR.
.TP
\fI-peer\fR
Returns the remote hostname and port number for the packet most recently
received by this socket.
.TP
\fI-broadcast ?boolean?\fR
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. This option is not permitted when
using IPv6.
.TP
\fI-ttl ?count?\fR
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.
.TP
\fI-mcastadd\fR groupaddr
.TP
\fI-mcastadd\fR "groupaddr netwif"
.TP
\fI-mcastdrop\fR groupaddr
.TP
\fI-mcastdrop\fR "groupaddr netwif"
.TP
\fI-mcastgroups\fR
\fBtcludp\fR sockets can support IPv4 and IPv6 multicast operations. To receive
multicast packets the application has to notify the operating system that
it should join a particular multicast group. For IPv4 these are specified as addresses
in the range 224.0.0.0 to 239.255.255.255.
.sp
When specifying only the \fIgroupaddr\fR the system will determine the network interface to use.
Specifying the \fInetwif\fR will join a multicast group on a specific network interface.
This is useful on a multihomed system with multiple network interfaces.
On windows you must specify the network interface index. For other platforms the network
interface (e.g. 'eth0') name can be specified.
.sp
To view the current set of multicast groups for a channel use \fI-mcastgroups\fR
.TP
\fI-mcastloop ?boolean?\fR
With multicast udp the system can choose to receive packets that it has sent
or it can drop them. This is known as multicast loopback and can be controlled
using this option. By default the value is true and your application will receive
its own transmissions.
.RE
.TP
\fBudp_peek\fR \fIsock\fR ?\fIbuffersize\fR?
Examine a packet without removing it from the buffer. Option \fIbuffersize\fR specifies the
maximum buffer size. Value must be between 0 and 16.
.sp
This function is not available on windows.
.PP
.SH EXAMPLES
.PP
.nf

# 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
}

.fi
.nf

# 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

.fi
.nf

# 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

.fi
.SH 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.
.PP
Enhancements to support binary data and to setup the package for the Tcl
Extension Architecture by Pat Thoyts.
.PP
Support for IPv6 and allowing a multicast join on a specific network interface is added by Huub Eikens.
.SH "SEE ALSO"
socket(3tcl)
.SH KEYWORDS
networking, socket, udp
.SH COPYRIGHT
.nf
Copyright (c) 1999-2000 Columbia University; all rights reserved

.fi