The easiest way to interact with Asterisk from Java applications is via the FastAGI protocol. AGI scripts can handle either incoming calls or calls originated via the Manager API (see below for an example on how to use Asterisk-Java to originate a call from your Java application).
The AGI (Asterisk Gateway Interface) facility allows you to launch scripts, from the Asterisk dial plan. Traditionally communication between the scripts and Asterisk was via standard input and standard output and scripts had to run on the same machine as Asterisk. Due to the large amount of time a Java Virtual Machine needs for startup and the discomfort of having to install a Java environment on the PBX box(es) Java has not been the language of choice for writing AGI scripts.
These drawbacks have been addressed by the addition of FastAGI to Asterisk. FastAGI is basically AGI over TCP/IP socket connections instead of using standard input and standard output as communication medium.
Using FastAGI you can run a Java application (on the same machine that runs Asterisk or on a seperate machine) that is only started once and serves AGI scripts until it is shut down. Combined with Java's multithreading support you can build pretty fast AGI scripts using this protocol.
Asterisk-Java helps you with running your Java based AGI scripts by providing a container that recives connections from the Asterisk server, parses the request and calls your scripts mapped to the called URL.
To write your own AGI scripts you must implement the AGIScript interface. You can do so by simply extending AbstractAGIScript that provides some convenience methods that further simplify that task.
A simple AGIScript might look as follows:
import net.sf.asterisk.fastagi.AGIChannel;
import net.sf.asterisk.fastagi.AGIException;
import net.sf.asterisk.fastagi.AGIRequest;
import net.sf.asterisk.fastagi.AbstractAGIScript;
public class HelloAGIScript extends AbstractAGIScript
{
public void service(AGIRequest request, AGIChannel channel)
throws AGIException
{
// Answer the channel...
answer(channel);
// ...say hello...
streamFile(channel, "welcome");
// ...and hangup.
hangup(channel);
}
}
If you are using Asterisk-Java 0.2 (or a snapshot thereof) you should extend BaseAGIScript instead of AbstractAGIScript. That way you don't have to pass the channel to all the methods as this is done automatically.
Put this Java source file into a directory of your choice,
add the asterisk-java.jar and compile it:
$ javac -cp asterisk-java.jar HelloAGIScript.java $
Next you have to add a call to your script to your dialplan in Asterisk.
You might want to add an extension 1300 to the default section of your
extensions.conf:
[default] ... exten => 1300,1,Agi(agi://localhost/hello.agi)
Replace localhost with the hostname of the machine that runs Asterisk-Java.
Be sure to reload Asterisk for this change to take effect. You can do so
by executing extensions reload on the Asterisk CLI.
Now you must map the script name hello.agi to the HelloAGIScript
we just created. By default this is done in a properties file called
fastagi-mapping.properties that must be on the classpath
when we start the AGIServer. In this case it looks like:
hello.agi = HelloAGIScript
Your directory should now contain the following files:
$ ls -l -rw-r--r-- 1 srt srt 163689 2005-03-11 22:07 asterisk-java.jar -rw-r--r-- 1 srt srt 26 2005-03-11 20:50 fastagi-mapping.properties -rw-r--r-- 1 srt srt 624 2005-03-11 22:07 HelloAGIScript.class -rw-r--r-- 1 srt srt 438 2005-03-11 20:50 HelloAGIScript.java
Finally we start the AGIServer:
$ java -cp asterisk-java.jar:. net.sf.asterisk.fastagi.DefaultAGIServer
You should see some logging output indicating that the AGIServer has been successfully started and is listening for incoming connections:
Mar 11, 2005 10:20:12 PM net.sf.asterisk.fastagi.DefaultAGIServer run INFO: Thread pool started. Mar 11, 2005 10:20:12 PM net.sf.asterisk.fastagi.DefaultAGIServer run INFO: Listening on *:4573.
When you call extension 1300 you will see the AGI script being launched:
Mar 11, 2005 10:22:47 PM net.sf.asterisk.fastagi.DefaultAGIServer run INFO: Received connection. Mar 11, 2005 10:22:47 PM net.sf.asterisk.fastagi.AGIConnectionHandler run INFO: Begin AGIScript HelloAGIScript on AGIServer-TaskThread-0 Mar 11, 2005 10:22:48 PM net.sf.asterisk.fastagi.AGIConnectionHandler run INFO: End AGIScript HelloAGIScript on AGIServer-TaskThread-0
Have a look at the documentation of AbstractAGIScript there you will find additional methods that you can use for your own scripts. If you want to use commands that do not yet have a corresponding method in AbstractAGIScript or if you want to extend the FastAGI protocol by adding your own commands you can also use the channel.sendCommand(AGICommand) method to send arbitrary commands.
You can pass parameters to your scripts by including them in the URL used with the AGI command. These parameters can be read by the getParameter(String) and getParameterValues(String) methods in AGIRequest.
If you want to pass a parameter named user with a value of "john" to your script called hello.agi running on localhost your call to the AGI application looks like this:
exten => 1300,1,Agi(agi://localhost/hello.agi?user=john)
You can also pass multiple parameters. Parameters containing special characters must be URL encoded.
If you are about to write more complex scripts please note that your AGIScript must be threadsafe. Only one instance will be used to serve all requests. This is kind of similar to the constraints a servlet engine places on the implementation of servlets.
You can tune the DefaultAGIServer by setting two properties: The bindPort and the poolSize.
The bindPort determines the TCP port the server will listen on. By default
this is the FastAGI port 4573. If you change it make sure to include the
new port in the URLs used in extensions.conf. When using
bindPort 1234 your extensions.conf will contain:
exten => 1300,1,Agi(agi://localhost:1234/hello.agi)
To understand the poolSize property you need to know that the DefaultAGIServer uses a fixed size thread pool to serve your AGIScripts. The poolSize determines how many threads are spawned at startup and thus limits the number of AGIScripts that can run at the same time. So you should set the poolSize to at least the number of concurrent calls the AGIServer should be able to handle. The default value is 10.
These configuration properties can be set by providing a
fastagi.properties file on the classpath.
This might look like:
bindPort = 1234 poolSize = 20
The Manager API is the other way for remote interaction with an Asterisk server. In contrast to the FastAGI protocol Asterisk does not explicitly pass control to your application when using the Manager API but allows you to query and change its state at any time.
The Manager API is made up of three concepts: Actions, Responses and Events.
Actions can be sent to Asterisk and instruct it to do someting. For example your application can send an Action to Asterisk requesting it to dial a number and direct the dialed party to one of your phones. In reply to an Action Asterisk sends a Reply that contains the results of the operation performed.
Events are sent by Asterisk without a direct relation to the Actions your application is sending. Events inform you about the relevant changes in Asterisk's state. For example Events are used to inform your application about incoming calls or users joining or leaving MeetMe conference rooms.
The connection to the Asterisk server via Manager API occurs over TCP/IP usually on the default port 5038.
To enable the Manager API on Asterisk you must edit your manager.conf
configuration file and restart Asterisk. The manager.conf also contains
constraints on the range of IP addresses that are allowed to connect and username
and passwords for authentication. A sample might look like:
[general] enabled = yes port = 5038 bindaddr = 0.0.0.0 [manager] secret=pa55w0rd permit=0.0.0.0/0.0.0.0 read=system,call,log,verbose,agent,command,user write=system,call,log,verbose,agent,command,user
This will enable the Manager AP, allow access from any IP address using the username "manager" and the password "pa55w0rd".
Assume we have a phone connected via SIP that is available at SIP/john and we want to initiate a call from that phone to extension 1300 in the default context.
We have to obtain a
ManagerConnection
providing the hostname Asterisk is running on and the username and password
as configured in manager.conf. Next we log in and send an
OriginateAction
and finally we disconnect.
An example that does this is shown below.
import java.io.IOException;
import net.sf.asterisk.manager.AuthenticationFailedException;
import net.sf.asterisk.manager.ManagerConnection;
import net.sf.asterisk.manager.ManagerConnectionFactory;
import net.sf.asterisk.manager.TimeoutException;
import net.sf.asterisk.manager.action.OriginateAction;
import net.sf.asterisk.manager.response.ManagerResponse;
public class HelloManager
{
private ManagerConnection managerConnection;
public HelloManager() throws IOException
{
ManagerConnectionFactory factory = new ManagerConnectionFactory();
this.managerConnection = factory.getManagerConnection("localhost",
"manager", "pa55w0rd");
}
public void run() throws IOException, AuthenticationFailedException,
TimeoutException
{
OriginateAction originateAction;
ManagerResponse originateResponse;
originateAction = new OriginateAction();
originateAction.setChannel("SIP/John");
originateAction.setContext("default");
originateAction.setExten("1300");
originateAction.setPriority(new Integer(1));
originateAction.setTimeout(new Integer(30000));
// connect to Asterisk and log in
managerConnection.login();
// send the originate action and wait for a maximum of 30 seconds for Asterisk
// to send a reply
originateResponse = managerConnection.sendAction(originateAction, 30000);
// print out whether the originate succeeded or not
System.out.println(originateResponse.getResponse());
// and finally log off and disconnect
managerConnection.logoff();
}
public static void main(String[] args) throws Exception
{
HelloManager helloManager;
helloManager = new HelloManager();
helloManager.run();
}
}
A list of the other Actions povided by the Manager API is available in the javadocs.
To receive events from Asterisk you have to implement the ManagerEventHandler interface and add it to the ManagerConnection
The following code shows a simple example of how to do this:
import java.io.IOException;
import net.sf.asterisk.manager.AuthenticationFailedException;
import net.sf.asterisk.manager.ManagerConnection;
import net.sf.asterisk.manager.ManagerConnectionFactory;
import net.sf.asterisk.manager.ManagerEventHandler;
import net.sf.asterisk.manager.TimeoutException;
import net.sf.asterisk.manager.action.StatusAction;
import net.sf.asterisk.manager.event.ManagerEvent;
public class HelloEvents implements ManagerEventHandler
{
private ManagerConnection managerConnection;
public HelloEvents() throws IOException
{
ManagerConnectionFactory factory = new ManagerConnectionFactory();
this.managerConnection = factory.getManagerConnection("localhost",
"manager", "pa55w0rd");
}
public void run() throws IOException, AuthenticationFailedException,
TimeoutException, InterruptedException
{
// register for events
managerConnection.addEventHandler(this);
// connect to Asterisk and log in
managerConnection.login();
// request channel state
managerConnection.sendAction(new StatusAction());
// wait 10 seconds for events to come in
Thread.sleep(10000);
// and finally log off and disconnect
managerConnection.logoff();
}
public void handleEvent(ManagerEvent event)
{
// just print received events
System.out.println(event);
}
public static void main(String[] args) throws Exception
{
HelloEvents helloEvents;
helloEvents = new HelloEvents();
helloEvents.run();
}
}
A list of the other Events povided by the Manager API is available in the javadocs.