This is a "plugin" for the Video Disk Recorder (VDR).

Written by:                  Lars Hanisch <dvb@flensrocker.de>

Project's homepage:          https://github.com/flensrocker/vdr-plugin-avahi4vdr

Latest version available at: https://github.com/flensrocker/vdr-plugin-avahi4vdr

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
See the file COPYING for more information.

Description:
With this plugin it is possible to announce network service via avahi
to the LAN. Also plugins can browse for services on the LAN.

Call avahi4vdr's SVDRPCommand directly to publish a service or to browse
for one. You'll get an string with something like "id=<uuid>" to identify
your service or browser.
avahi4vdr will send events through the plugin's Service function if something
happens to your service or browser.

Here is some pseudo code for controlling avahi4vdr like dbus2vdr will use it.

Publish network service
-----------------------
  int replyCode = 0;
  cString serviceId;
  cPlugin *avahi4vdr = cPluginManager::GetPlugin("avahi4vdr");
  ...
  if (avahi4vdr != NULL)
     serviceId = avahi4vdr->SVDRPCommand("CreateService", "caller=dbus2vdr,name=dbus2vdr,protocol=IPv4,port=12345,type=_dbus._tcp,subtype=_vdr_dbus2vdr._sub._dbus._tcp", replyCode);
  ...
  if (replyCode == 900)
     avahi4vdr->SVDRPCommand("DeleteService", *serviceId, replyCode);

Browse for network services
---------------------------
  // for a real worl example, lookup dbus2vdr in its git
  int replyCode = 0;
  cString browserId;
  cPlugin *avahi4vdr = cPluginManager::GetPlugin("avahi4vdr");
  ...
  if (avahi4vdr != NULL)
     browserId = avahi4vdr->SVDRPCommand("CreateBrowser", "caller=dbus2vdr,protocol=IPv4,type=_vdr_dbus2vdr._sub._dbus._tcp", replyCode);
  ...
  if (replyCode == 900)
     avahi4vdr->SVDRPCommand("DeleteBrowser", *browserId, replyCode);
  ...
  bool cPluginDbus2vdr::Service(const char *Id, void *Data)
  {
    if (strcmp(Id, "avahi4vdr-event") == 0) {
       cAvahiHelper options((const char*)Data);
       const char *event = options.Get("event");
       const char *browser_id = options.Get("id");
       if (strcmp(event, "browser-service-resolved") == 0) {
          const char *name = options.Get("name");
          const char *host = options.Get("host");
          const char *protocol = options.Get("protocol");
          const char *address = options.Get("address");
          const char *port = options.Get("port");
          const char *local = options.Get("local");
          const char *txt = NULL;
          int txt_nr = 0;
          while (true) {
                txt = options.Get("txt", txt_nr);
                if (txt == NULL)
                   break;
                ...
                txt_nr++;
                }
          ...
          }
       else if (strcmp(event, "browser-service-removed") == 0) {
          const char *name = options.Get("name");
          const char *protocol = options.Get("protocol");
          const char *local = options.Get("local");
          ...
          }
       return true;
       }
    return false;
  }

Parameters
----------
Every call to avahi4vdr expects a string with comma separated key/value-pairs like
"key1=value1,key2=value2,key3=value3,..."

If a key or value contains a comma or backslash, it has to be escaped with a backslash.
"name=dbus2vdr, host vdr" must be "name=dbus2vdr\, host vdr"
You should use vdr's function 'cString esc_name = strescape(name, "\\,");' to get a
correctly escaped string.

You can use avahi-helper.h for a class that splits up the parameter string into the
single key/value pairs.

The returned strings of SVDRPCommand may contain the following keys:
id:      uuid of the service or browser you created
error:   error message, e.g. if parameters are missing
message: success message

Events
------
If avahi4vdr notices that something "happens" to your services or browsers it will call
the Service function of the plugin with the name of the parameter "caller" given to
"CreateService" or "CreateBrowser".
The first parameter will be "avahi4vdr-event" and the second a key/value-list in the
format mentioned above.

Service events
--------------
* event=service-created,id=a328227c-a1e7-45f8-8062-6e9f81395f90
  Your service has been created by "CreateService" but has not been published yet.

* event=service-started,id=a328227c-a1e7-45f8-8062-6e9f81395f90
  Your service is published by the avahi-daemon.

* event=service-stopped,id=a328227c-a1e7-45f8-8062-6e9f81395f90
  Publishing of your service has been stopped. This may occur if avahi4vdr gets some error
  from the avahi-daemon or if the avahi-daemon stopps.
  avahi4vdr will try to reconnect to the daemon and will publish your services again.
  You don't have to do anything.

* event=service-deleted,id=a328227c-a1e7-45f8-8062-6e9f81395f90
  Your service has been deleted through a call of "DeleteService" or halt of vdr.

Browser events
--------------
* event=browser-created,id=a3c43ebb-be1d-4312-908f-2a78c91a062b
  You (or someone using your plugin's name) created a browser with "CreateBrowser".

* event=browser-started,id=a3c43ebb-be1d-4312-908f-2a78c91a062b
  The browser is started and will get notified if it discovers something matching your browser's data.

* event=browser-service-resolved,id=a3c43ebb-be1d-4312-908f-2a78c91a062b,name=dbus2vdr on vdr,type=_dbus._tcp,protocol=IPv6,address=fe80::223:54ff:fe2f:4712,host=vdr.local,port=59419,local=true
* event=browser-service-resolved,id=a3c43ebb-be1d-4312-908f-2a78c91a062b,name=dbus2vdr on vdr,type=_dbus._tcp,protocol=IPv4,address=192.168.23.13,host=vdr.local,port=59419,local=true
  Congratulations, you discovered a network service!

* event=browser-allfornow,id=a3c43ebb-be1d-4312-908f-2a78c91a062b
  Avahi doesn't expect any new services in the near future.

* event=browser-service-removed,id=a3c43ebb-be1d-4312-908f-2a78c91a062b,name=dbus2vdr on vdr,type=_dbus._tcp,protocol=IPv4,local=true
* event=browser-service-removed,id=a3c43ebb-be1d-4312-908f-2a78c91a062b,name=dbus2vdr on vdr,type=_dbus._tcp,protocol=IPv6,local=true
  The service is not longer available.

* event=browser-stopped,id=a3c43ebb-be1d-4312-908f-2a78c91a062b
  Like "serivce-stopped", see above.

* event=browser-deleted,id=a3c43ebb-be1d-4312-908f-2a78c91a062b
  Like "browser-stopped", see above.

services.conf
-------------
You can place a file called services.conf in the plugin's configuration directory.
For each valid line with a service configuration, this service will be published
via the avahi-daemon. Each occurrence of "%h" will be replaced with the hostname.
You should use the following scheme for the subtypes:
  _vdr_<pluginname>._sub._<protocol>._<transport>

Examples:
name=SVDRP on %h,type=_svdrp._tcp,port=6419
name=vdr-live on %h,type=_https._tcp,port=8443,subtype=_vdr_live._sub._https._tcp
name=streamdev-server on %h,type=_http._tcp,port=3000,subtype=_vdr_streamdevserver._sub._http._tcp

To reload the services.conf there's the SVDRP command "ReloadServices".