From 70f08a7afb001c7c1608181fa4546c6460890e04 Mon Sep 17 00:00:00 2001 From: markster Date: Thu, 16 Dec 1999 12:59:53 +0000 Subject: Version 0.1.1 from FTP git-svn-id: http://svn.digium.com/svn/asterisk/trunk@138 f38db490-d61c-443f-a65b-d21fe96a405b --- doc/channel.txt | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100755 doc/channel.txt (limited to 'doc') diff --git a/doc/channel.txt b/doc/channel.txt new file mode 100755 index 000000000..4cef6a4c6 --- /dev/null +++ b/doc/channel.txt @@ -0,0 +1,40 @@ +Implementing a Channel +====================== + +* What is a channel? + +A channel is a unit which brings in a call to the Asterisk PBX. A channel +could be connected to a real telephone (like the Internet Phone Jack) or +to a logical call (like an Internet phone call). Asterisk makes no +distinction between "FXO" and "FXS" style channels (that is, it doesn't +distinguish between telephone lines and telephones). + +Every call is placed or received on a distinct channel. Asterisk uses a +channel driver (typically named chan_xxx.so) to support each type of +hardware. + +* What do I need to create a channel? + +In order to support a new piece of hardware you need to write a channel +driver. The easiest way to do so is to look at an existing channel driver +and model your own code after it. + +* What's the general architecture? + +Typically, a channel reads a configuration file on startup which tells it +something about the hardware it's going to be servicing. Then, it +launches a thread which monitors all the idle channels (See the chan_modem +or the chan_ixj for an example of this). When a "RING" or equivalent is +detected, the monitoring thread should allocate a channel structure and +assign all the callbacks to it (see ixj_new, for example), and then call +ast_pbx_start on that channel. ast_pbx_start will launch a new thread to +handle the channel as long as the call is up, so once pbx_start has +successfully been run, the monitor should no longer monitor that channel. +The PBX thread will use the channel, reading, writing, calling, etc., and +multiplexing that channel with others using select() on the channel's +file descriptor (if your channel doesn't have an associated file +descriptor, you'll need to emulate one somehow, perhaps along the lines of +what the translator API does with its channel. + +When the PBX is finished with the line, it will hang up the line, at which +point it the hardware should again be monitored by the monitoring thread. -- cgit v1.2.3