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udp: Create UDP sockets in Tcl

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. (//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 UDP(3)
 
 
 

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