# &adminguide;

## Overview

The EVAPI module can be used to create an event message flow from Kamailio to any application that can connect to a TCP socket. The remote application can also issue messages received by Kamailio.

There is no protocol definition, it is all up to the author of the routing script. Events can be generated for any event in Kamailio. For 3rd party transaction control, a transaction can be automatically suspended when sending the event, to be resumed at a later point, maybe triggered by an incoming message on the event socket.

## Dependencies

### &kamailio; Modules

The following modules must be loaded before this module:

- tm - (optional) needed only by evapi_async_relay()

### External Libraries or Applications

The following libraries or applications must be installed before running &kamailio; with this module loaded:

- libev - http://software.schmorp.de/pkg/libev

## Parameters

### `workers` (int)

Number of worker processes to be started to handle incoming messages from remote applications. If the value is 0, the handling of the incoming message is done by the evapi dispatcher process.

Default value is 1.

#### Set `workers` parameter

    ...
    modparam("evapi", "workers", 2)
    ...

### `bind_addr` (str)

Local IP and port to listen on for incoming TCP connections.

Default value is "127.0.0.1:8448".

#### Set `bind_addr` parameter

    ...
    modparam("evapi", "bind_addr", "1.2.3.4:8228")
    ...

### `netstring_format` (int)

Control if messages on the socket (to and from clients) are encapsulated in netstring format.

Default value is 1 (netstring format).

#### Set `netstring_format` parameter

    ...
    modparam("evapi", "netstring_format", 0)
    ...

### `event_callback` (str)

The name of the function in the kemi configuration file (embedded scripting language such as Lua, Python, ...) to be executed instead of event_route[...] blocks.

The function receives a string parameter with the name of the event, the values are: 'evapi:connection-new', 'evapi:connection-closed', 'evapi:message-received'.

Default value is 'empty' (no function is executed for events).

#### Set `event_callback` parameter

    ...
    modparam("evapi", "event_callback", "ksr_evapi_event")
    ...
    -- event callback function implemented in Lua
    function ksr_evapi_event(evname)
    	KSR.info("===== evapi module triggered event: " .. evname .. "\n");
    	return 1;
    end
    ...

### `max_clients` (int)

Maximum number of clients that can connect to evapi socket.

Default value is 8.

#### Set `max_clients` parameter

    ...
    modparam("evapi", "max_clients", 4)
    ...

### `wait_idle` (int)

How many micro-seconds to wait on idle, when no evapi messages are in the processing queue.

Default value is 500 000 (0.5 seconds).

#### Set `wait_idle` parameter

    ...
    modparam("evapi", "wait_idle", 100000)
    ...

### `wait_increase` (int)

Increase wait_idle by itself till its value becomes initial value multiplied with wait_increase. The increase is done only consecutive cycles without any evapi message. When a new evapi message is received, wait_idle is reset to initial value. If wait_increase is set to 1, then wait_idle is used with its initial value always.

Default value is 3.

#### Set `wait_increase` parameter

    ...
    modparam("evapi", "wait_increase", 1)
    ...

## Functions

### `evapi_relay(evdata)`

Relay the event data given as parameter to connected applications.

The format on the network is netstring with evdata payload if netstring_format parameter is set to 1 or bare evdata if netstring_format parameter is set to 0.

The function is passing the task to evapi dispatcher process, therefore the SIP worker process is not blocked. Also, it doesn't wait for any response, therefore the processing of the configuration continues very fast when executing evapi_relay().

This function can be used from ANY_ROUTE.

#### `evapi_relay` usage

    ...
    evapi_relay("{ \"event\": \"test\",\n \"data\": { \"fU\": \"$fU\" }\n}");
    ...

The above example will send the following message over tcp:

#### TCP message

    ...
    47:{
     "event": "test",
     "data": { "fU": "test" }
    },
    ...

### `evapi_async_relay(evdata)`

Relay the event data given as parameter to connected applications. Before evaluating the parameter, the request processing is suspended using tm module (using the t_suspend()/t_continue() framework). The routing of the SIP request can be continued once event_route[evapi:message-received] is triggered. After evapi_async_relay() returns true, no relaying should happen in request_route(), it should be followed by exit;.

The format on the network is netstring with evdata payload if netstring_format parameter is set to 1 or bare evdata if netstring_format parameter is set to 0.

This function can be used from REQUEST_ROUTE.

#### `evapi_async_relay` usage

    ...
    evapi_async_relay("{ \"event\": \"suspend\",\n \"data\":"
            " { \"index\": \"$T(id_index)\", \"label\": \"$T(id_label)\" }\n}");
    ...

### `evapi_multicast(evdata, etag)`

Relay the event data given as parameter to connections that match the tag provided by etag value. The etag can be a variable. For more see evapi_relay() and evapi_set_tag().

#### `evapi_multicast` usage

    ...
    evapi_multicast("{ \"event\": \"test\",\n \"data\": { \"fU\": \"$fU\" }\n}", "tagx");
    ...

### `evapi_async_multicast(evdata, etag)`

Async relay the event data given as parameter to connections that match the tag provided by etag value. The etag can be a variable. For more see evapi_async_relay() and evapi_set_tag().

#### `evapi_async_multicast` usage

    ...
    evapi_async_multicast("{ \"event\": \"suspend\",\n \"data\":"
        " { \"index\": \"$T(id_index)\", \"label\": \"$T(id_label)\" }\n}", "tagx");
    ...

### `evapi_unicast(evdata, etag)`

Relay the event data given as parameter to the first connection that match the tag provided by etag value. The etag can be a variable. For more see evapi_relay() and evapi_set_tag().

#### `evapi_unicast` usage

    ...
    evapi_unicast("{ \"event\": \"test\",\n \"data\": { \"fU\": \"$fU\" }\n}", "tagx");
    ...

### `evapi_async_unicast(evdata, etag)`

Async relay the event data given as parameter to the first connection that match the tag provided by etag value. The etag can be a variable. For more see evapi_async_relay() and evapi_set_tag().

#### `evapi_async_unicast` usage

    ...
    evapi_async_unicast("{ \"event\": \"suspend\",\n \"data\":"
        " { \"index\": \"$T(id_index)\", \"label\": \"$T(id_label)\" }\n}", "tagx");
    ...

### `evapi_close()`

Close evapi current client connection.

This function can be used from ANY_ROUTE.

#### `evapi_close` usage

    ...
    event_route[evapi:connection-new] {
      if($evapi(srcaddr)!="127.0.0.1") {
        evapi_close();
        exit;
      }
    }
    ...

### `evapi_set_tag(tname)`

Set tag name for current client connection. The parameters has to be a string up to 64 characters. It can also be a variable holding such string.

This function can be used from ANY_ROUTE.

#### `evapi_set_tag` usage

    ...
    event_route[evapi:connection-new] {
      if($evapi(srcaddr)=="127.0.0.1") {
        evapi_set_tag("local");
        exit;
      }
    }
    ...

## Event routes

### `evapi:connection-new`

If defined, the module calls event_route[evapi:connection-new] when a new client is connected.

    ...
    event_route[evapi:connection-new] {
        xlog("new connection from $evapi(srcaddr):$evapi(srcport)\n");
    }
    ...

### `evapi:connection-closed`

If defined, the module calls event_route[evapi:connection-closed] when a client connection is closed.

    ...
    event_route[evapi:connection-closed] {
        xlog("connection closed by $evapi(srcaddr):$evapi(srcport)\n");
    }
    ...

### `evapi:message-received`

If defined, the module calls event_route[evapi:message-received] when a message is received from a client.

    ...
    event_route[evapi:message-received] {
        xlog("received [$evapi(msg)] from $evapi(srcaddr):$evapi(srcport)\n");
    }
    ...

## Exported pseudo-variables

- $evapi(srcaddr) - source ip

- $evapi(srcport) - source port

- $evapi(msg) - received event message

- $evapi(conidx) - internal connection index

Exported pseudo-variables are documented at &kamwikilink;.