# &adminguide;

## Overview

The SIGNALING module comes as a wrapper over tm and sl modules and offers one function to be called by the modules that want to send a reply.

The logic behind the module is to first search if a transaction is created and if so, send a state full reply, using tm module, otherwise send a stateless reply with the function exported by sl. In this way, the script writer still has the call on how the transaction should be handled, state full or stateless and the reply is send accordingly to his choice.

For example, if you do a t_newtran() in the script before doing save() (for registration), the function will automatically send the reply in stateful mode as a transaction is available. If no transaction is done, the reply will be sent in stateless way (as now).

By doing this, we have the possibility to have same module sending either stateful either stateless replies, by just controlling this from the script (if we create or not a transaction). So, the signalling will be more coherent as the replies will be sent according to the transaction presence (or not).

Moreover, this module offers the possibility of loading only one of the module, sl or tm, and send reply using only the module that is loaded. This is useful as not in all cases a user desires to send stateful or stateless replies and he should not be forced to load the module only because the send reply interface requires it.

## Dependencies

### &osips; Modules

At least one of the following modules must be loaded before this module:

- sl.

- tm.

### External Libraries or Applications

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

- None.

## Exported Parameters

- None.

## Exported Functions

### `send_reply(code, reason)`

For the current request, a reply is sent back having the given code and text reason. The reply is sent stateless or statefull depending on which module is loaded and if a transaction was created, as explained above.

Meaning of the parameters is as follows:

- code - Return code.

- reason - Reason phrase.

This function can be used from REQUEST_ROUTE, ERROR_ROUTE.

#### `sl_send_reply` usage

    ...
    send_reply("404", "Not found");
    ...
    send_reply("$err.rcode", "$err.rreason");
    ...