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- SAMP (Simple Application Messaging Protocol) (`astropy.samp`)

# SAMP (Simple Application Messaging Protocol) (`astropy.samp`)

`astropy.samp` is a Python implementation of the SAMP messaging system.

Simple Application Messaging Protocol (SAMP) is an inter-process communication system that allows different client programs, usually running on the same computer, to communicate with each other by exchanging short messages that may reference external data files. The protocol has been developed within the International Virtual Observatory Alliance (IVOA) and is understood by many desktop astronomy tools, including TOPCAT, SAO DS9, and Aladin.

So by using the classes in `astropy.samp`, Python code can interact with other running desktop clients, for instance displaying a named FITS file in DS9, prompting Aladin to recenter on a given sky position, or receiving a message identifying the row when a user highlights a plotted point in TOPCAT.

The way the protocol works is that a SAMP “Hub” process must be running on the local host, and then various client programs can connect to it. Once connected, these clients can send messages to each other via the hub. The details are described in the SAMP standard.

`astropy.samp` provides classes both to set up such a hub process, and to help implement a client that can send and receive messages. It also provides a stand-alone program `samp_hub` which can run a persistent hub in its own process. Note that setting up the hub from Python is not always necessary, since various other SAMP-aware applications may start up a hub independently; in most cases, only one running hub is used during a SAMP session.

The following classes are available in `astropy.samp`:

- `SAMPHubServer`, which is used to instantiate a hub server that clients can then connect to.

- `SAMPHubProxy`, which is used to connect to an existing hub (including hubs started from other applications such as TOPCAT).

- `SAMPClient`, which is used to create a SAMP client.

- `SAMPIntegratedClient`, which is the same as `SAMPClient` except that it has a self-contained `SAMPHubProxy` to provide a simpler user interface.

`astropy.samp` is a full implementation of SAMP V1.3. As well as the Standard Profile, it supports the Web Profile, which means that it can be used to also communicate with web SAMP clients; see the sampjs library examples for more details.

## Using `astropy.samp`

- Starting and Stopping a SAMP Hub Server
  - Using an Existing Hub
  - Using the Command-Line Hub Utility
  - Starting a Hub Programmatically (Advanced)
- Sending and Receiving Tables and Images over SAMP
  - Sending a Table to TOPCAT and DS9
  - Receiving a Table from TOPCAT
  - Example
  - Sending an Image to DS9 and Aladin
  - Receiving a Table from DS9 or Aladin
- Communication between Integrated Clients Objects
- Embedding a SAMP Hub in a GUI
  - Overview

## Reference/API

### astropy.samp Package

This subpackage provides classes to communicate with other applications via the Simple Application Messaging Protocol (SAMP).

Before integration into Astropy it was known as SAMPy, and was developed by Luigi Paioro (INAF - Istituto Nazionale di Astrofisica).

#### Classes

`Conf`() | Configuration parameters for `astropy.samp`.
`SAMPClient`(hub[, name, description, ...]) | Utility class which provides facilities to create and manage a SAMP compliant XML-RPC server that acts as SAMP callable client application.
`SAMPClientError` | SAMP Client exceptions.
`SAMPHubError` | SAMP Hub exception.
`SAMPHubProxy`() | Proxy class to simplify the client interaction with a SAMP hub (via the standard profile).
`SAMPHubServer`([secret, addr, port, ...]) | SAMP Hub Server.
`SAMPIntegratedClient`([name, description, ...]) | A Simple SAMP client.
`SAMPMsgReplierWrapper`(cli) | Function decorator that allows to automatically grab errors and returned maps (if any) from a function bound to a SAMP call (or notify).
`SAMPProxyError`(faultCode, faultString, **extra) | SAMP Proxy Hub exception
`SAMPWarning` | SAMP-specific Astropy warning class
`WebProfileDialog`() | A base class to make writing Web Profile GUI consent dialogs easier.

#### Class Inheritance Diagram

## Acknowledgments

This code is adapted from the SAMPy package written by Luigi Paioro, who has granted the Astropy Project permission to use the code under a BSD license.