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Matlab-CosmosC2

WebApi

CosmosJsonApi and CosmosJsonRpcApi are both interfaces that make it easier to get data from Cosmos v5 to Matlab.

Example:

setenv('COSMOS_API_SCHEMA', 'http')
setenv('COSMOS_API_HOST', 'localhost')
setenv('COSMOS_API_PORT', '2900')
setenv('COSMOS_API_PASSWORD', 'password')

api = CosmosJsonApi();

status = api.status();

disp(status);

WebSockets

matlab-cosmosc2 is a simple library consisting of a client for MATLAB built on Java-WebSocket, a java implementation of the websocket protocol. Encryption is supported with self-signed certificates made with the java keytool.

Installation and Uninstallation

IMPORTANT: you must make sure to install the java library to the static class path by following the instructions below. matlab-cosmosc2 will not work otherwise!

First, download the latest release on GitHub and extract the contents where you want.

The required java library is a jar file located in the /jar/ folder. It must be placed on the static java class path in MATLAB. For example, if the location of the jar file is C:\git\matlab-cosmosc2\jar\matlab-cosmosc2-*.*.jar, then open the static class path file with the following command:

edit(fullfile(prefdir,'javaclasspath.txt'))

and add the path to where you stored the jar C:\git\matlab-cosmosc2\jar\matlab-cosmosc2-*.*.jar to it. Make sure that there are no other lines with a matlab-cosmosc2-* entry.

Make sure to replace the stars matlab-cosmosc2-*.*.jar with the correct version number that you downloaded.

After having done this, restart MATLAB and check that the line was read by MATLAB properly by running the javaclasspath command. The line should appear at the bottom of the list, before the DYNAMIC JAVA PATH entries. Note that seeing the entry here does not mean that MATLAB necessarily found the jar file properly. You must make sure that the actual jar file is indeed at this location.

You must now add the /src/ folder to the MATLAB path. If you want to run the examples, add the /examples/ folder as well.

Simply undo these operations to uninstall MatlabWebSocket.

See the MATLAB Documentation for more information on the static java class path.

Usage

To implement a WebSocket server or client, a subclass of either WebSocketServer or WebSocketClient must be defined. For more details (see the object-oriented programming documentation of MATLAB).

The CosmosWebSocketClient.m file is an abstract MATLAB class. The behavior of the server must therefore be defined by creating a subclass that implements the following methods:

onOpen(obj,conn,message)
onTextMessage(obj,conn,message)
onBinaryMessage(obj,conn,message)
onError(obj,conn,message)
onClose(obj,conn,message)
  • obj is the object instance of the subclass, it is implicitly passed by MATLAB (see the object-oriented programming documentation of MATLAB).
  • message is the message received by the server. It will usually be a character array, except for the onBinaryMessage method, in which case it will be an int8 array

These methods will be automatically called when the corresponding event (connection is opened, message received, etc...) occurs. In this way, a reactive behavior can be defined.

See the test.m files in the examples folder for an implementation example. A good resource on classes is the MATLAB object-oriented documentation.

Example

Connecting to Cosmos v5 with the CosmosClient:

SCHEMA = 'wss';
HOST = 'cosmos';
PORT = 2900;
ENDPOINT = '/cosmos-api/cable';
AUTH = 'password';
client = CosmosWebSocket(SCHEMA,HOST,PORT,ENDPOINT,AUTH);

or make sure you have your environment loaded with

setenv('COSMOS_WS_SCHEMA', 'wss')
setenv('COSMOS_API_HOST', 'cosmos')
setenv('COSMOS_API_PORT', '2900')
setenv('COSMOS_API_PASSWORD', 'password')

client = CosmosWebSocket();

SSL / WebSocket Secure (wss)

To enable SSL, you must first have a certificate. A self-signed key store can be generated with the java keytool, but you should always use a valid certificate in production. From there, open the server by passing the location of the store, the store password, and the key password. With the CosmosWebSocketClient, for example:

The client can then connect to it:

URI = 'wss://localhost:2900/cosmos-api/cable';
c = CosmosWebSocketClient(URI,STORE,STOREPASSWORD,KEYPASSWORD);

Building the Java JAR

To build the jar file yourself, it is recommended to use Apache Maven. Maven will automatically take care of downloading Java-WebSocket and neatly package everything into a single file (an "uber jar").

If you are running on a network behind a firewall intercepting SSL certificates use these...

-Djavax.net.ssl.trustStore=
-Dmaven.wagon.http.ssl.insecure=true
-Dmaven.wagon.http.ssl.allowall=true
-Dmaven.wagon.http.ssl.ignore.validity.dates=true

Once the mvn command is on your path, simply cd to the matlab-cosmosc2 folder and execute mvn package.

Acknowledgments

This work was based on a MATLAB websocket implementation: MatlabWebSockets.

This work was inspired by a websocket client MATLAB implementation: matlab-websockets.

It relies on the Java-WebSocket library.

License

The code in this repository is licensed under the MIT license. See the LICENSE file for details.