It can have the following values −Ī value of 0 indicates that the connection has not yet been established.Ī value of 1 indicates that the connection is established and communication is possible.Ī value of 2 indicates that the connection is going through the closing handshake.Ī value of 3 indicates that the connection has been closed or could not be opened. The readonly attribute readyState represents the state of the connection. Assuming we created Socket object as mentioned above − Sr.No. WebSocket Attributesįollowing are the attribute of WebSocket object. The second attribute, protocol is optional, and if present, specifies a sub-protocol that the server must support for the connection to be successful. Here first argument, url, specifies the URL to which to connect. Once you get a Web Socket connection with the web server, you can send data from browser to server by calling a send() method, and receive data from server to browser by an onmessage event handler.įollowing is the API which creates a new WebSocket object. Section 5.4 of the spec describes message fragmentation.WebSockets is a next-generation bidirectional communication technology for web applications which operates over a single socket and is exposed via a JavaScript interface in HTML 5 compliant browsers. All remaining parts of that message are sent with continuation frames ( opcode=0x0), and the final frame of the message is marked by FIN=1. The second frame sent by the client has a text payload ( opcode=0x1), but the entire message has not arrived yet ( FIN=0). Notice the first frame contains an entire message (has FIN=1 and opcode!=0x0), so the server can process or respond as it sees fit. Server: (process complete message) Happy new year to you too!
Server: (listening, payload concatenated to previous message) Server: (listening, new message containing text started)Ĭlient: FIN=0, opcode=0x0, msg="happy new" Server: (process complete message immediately) Hi.
FIN and opcode details are shown only for the client: Client: FIN=1, opcode=0x1, msg="hello" The first message is sent in a single frame, while the second message is sent across three frames. Here is a rough sketch, in which a server reacts to a client sending text messages. However, if it's 0x0, the frame is a continuation frame this means the server should concatenate the frame's payload to the last frame it received from that client. Recall that the opcode tells what a frame is meant to do. Fragmentation is only available on opcodes 0x0 to 0x2. The FIN and opcode fields work together to send a message split up into separate frames. If it's 0, then the server keeps listening for more parts of the message otherwise, the server should consider the message delivered. The FIN bit tells whether this is the last message in a series.
In this version of WebSockets, 0x3 to 0x7 and 0xB to 0xF have no meaning.
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The opcode field defines how to interpret the payload data: 0x0 for continuation, 0x1 for text (which is always encoded in UTF-8), 0x2 for binary, and other so-called "control codes" that will be discussed later. RSV1-3 can be ignored, they are for extensions. Note: You must mask messages even when using a secure socket. (In fact, section 5.1 of the spec says that your server must disconnect from a client if that client sends an unmasked message.) When sending a frame back to the client, do not mask it and do not set the mask bit. Messages from the client must be masked, so your server must expect this to be 1.
The MASK bit tells whether the message is encoded. | Masking-key (continued ) | Payload Data | | Extended payload length continued, if payload len = 127 |
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