trusty (3) udp.3tcl.gz

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(3tcl)

KEYWORDS

       networking, socket, udp

COPYRIGHT

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