udp - Create UDP sockets in Tcl
+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.
+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.
+Using this keyword sets the SO_REUSEADDR socket option which permits multiple sockets to +be bound to the same address/port combination.
By default a IPv4 socket is created. When keyword ipv6 is specified an IPv6 +socket is opened.
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.
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.
+Returns the local port number of the socket.
Returns the remote hostname and port number as set using +udp_conf sock host port.
Returns the remote hostname and port number for the packet most recently +received by this socket.
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.
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.
tcludp 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.
+When specifying only the groupaddr the system will determine the network interface to use. +Specifying the netwif 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.
+To view the current set of multicast groups for a channel use -mcastgroups
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.
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.
+# 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
+
+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.
+socket(n)
+networking, socket, udp
+Copyright © 1999-2000 Columbia University; all rights reserved
+