WebSockets Learning Objectives

WebSockets enable two-way communication between the user’s browser (the client) and a server. They can be used to enable dynamic, interactive web experiences. After reading and practicing, 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
• Create a WebSocket onclose event handler function to detect when the connection to the server has been closed
• Use the ws package to create a standalone WebSocket server
• Use the ws package to create a WebSocket server that shares a Node.js http server with an Express application
• Create an connection event handler listener method to detect when a client has connected to the WebSocket server
• Create an close event handler listener method to detect when a client has closed the connection to the WebSocket server
• Use the WebSocket send() method to send a message to a client