WebSocket Client Applications

WebSockets enable two-way communication between the user’s browser (the client) and a server. Normally, the server only responds to client requests. When using WebSockets, once the client has opened a connection with the server, the server can send messages to the client.

A good place to start learning about Websockets on the Web is with the Writing WebSocket client applications article on MDN web docs.

After reading this article, you should be able to:

• Use the WebSockets API to create a new WebSocket connection to a server;
• Create a WebSocket onopen event handler function to detect when the connection has been opened;
• Create a WebSocket onmessage event handler function to detect and process messages sent by the server;
• Create a WebSocket onerror event handler function to detect when an error has occurred;
• Use the WebSocket send() method to send messages to the server;
• Recall that WebSocket message data can be sent as JSON formatted string;
• Recall that WebSocket messages usually have a “type” associated with them so the client can determine how to process them;
• Use the WebSocket close() method to close the connection to the server; and
• Create a WebSocket onclose event handler function to detect when the connection to the server has been closed.