WebSocket

This section covers general WebSocket communication with the MDS Server. Due to its microservice-architecture and communicating with many services, adjustments in WebSocket communication were needed. Therefore, an approach was chosen that allows communicating with multiple ones over the same WebSocket connection. When initiating a connection, it is made for a certain so called gate. Internally, a gate is configured to use a certain number of services. The WebSocket-Hub holds the connection to the client and negotiates between these services. This is done through channels. Each message is of the following format:

{
    "channel": "<channel_name>",
    "payload": {}
}

Based on the channel, the hub will forward to the correct service and for messages from a service, the channel will be set accordingly.

Authentication

Authentication via HTTP request headers when initiating the WebSocket connection is not possible with the Browser WebSocket API. Therefore, the first client message over the WebSocket connection is expected to consist of the authentication token. This message must not be in the format described above but in plain-text.