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Called when the WebSocket closesUsually, errors happen because of bad/malformed incoming packets. The <code>path</code> specifies WebSocket connection gets closed after the path which a client is connected toerror handling.
The WebSocket is already closed when this annotation is called so there can be no return. ==%ws:close(path)==
==%wsCalled when the WebSocket closes. The <code>path</code> specifies the path which a client is connected to:error(path, message)==
Called when an error occurs. The <codepre class="brush:xquery">pathdeclare %ws:close('/') function local:connect() { };</codepre> specifies the path which a client is connected to.
Usually, errors happen because of bad/malformed incoming packets. The <code>message</code> WebSocket is the error message. The WebSocket connection gets already closed after the error handlingwhen this annotation is called so there can be no return.
* The [[WebSocket Module]] contains functions for interacting with other clients or manage specific clients.* The results of functions annotated with If you get the <code>%[basex:ws:close] WebSocket connection required</code> or <code>%ws:error</code> will not , you may be transmitted attempting to the client.* For keeping the connection alive it is recommendable to use heartcall WebSocket functions from a non-beats, and send regular pings to the server.* Use <code>wss</code> instead of <code>ws</code> for a secure WebSocket connectioncontext.* If you use a proxy server, check in the configuration if WebSockets are enabled.
There are no heartbeats in this exampleWebSockets werre introduced with Version 9. This means that the connection is terminated if nothing happens for 5 minutes (standard timeout). It will also be closed if you send a message that exceeds the standard text size1.
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This page presents one of the [[Web Application]] services. It describes how to use the WebSockets API of BaseX. WebSocket is a communication protocol for providing '''full-duplex''' communication: Data can be sent in both directions and simultaneously.
Please note that the current WebSocket implementation relies on Jetty’s WebSocket servlet API. Other web servers may be supported in future versions.
=Introduction=
==%ws:connect(path)==
Called directly after a successful WebSocket handshake. The <code>path</code> specifies the path which a client is connected to.: <pre class="brush:xquery">declare %ws:connect('/') function local:connect() { };</pre>
You can specify here how to handle your users, e. g. save a name as a WebSocket attribute. Furthermore, you can check header parameters for validity.
==%ws:message(path, message)==
Called when a <code>client message</code> arrives at the server. The <code>path</code> specifies the path which a client is connected to.The <code>message</code> string contains the name of the variable to which the message will be bound: <pre class="brush:xquery">declare %ws:message('/', '{$info}') function local:message($info) { };</pre> The value will be of type <code>xs:string</code> or <code>xs:base64Binary</code>. As there is no fixed message protocol, the client needs to take care of the message syntax. ==%ws:error(path, message)==
Called when an error occurs. The <code>messagepath</code> specifies the path which a client is the connected to. The <code>message</code> sent by string contains the client. It will be name of type <code>xs:string</code> or <code>xs:base64Binary</code>. The client needs the variable to take care of which the message syntax, and it must not exceed the configured maximum size.will be bound:
<pre class=="brush:xquery">declare %ws:closeerror(path'/', '{$error}')==function local:error($error) { };</pre>
==%ws:header-param(name, variable[, default])==
For accessing connection-specific properties like the HTTP version. The value will be bound to the specified <code>variable</code>. If the property has no value is available, an optional <code>default</code> value will be bound assigned instead.: <pre class="brush:xquery">declare %ws:close('host', '{$host}') %ws:header-param('host', '{$host}')function local:close($host) { admin:write-log('Connection was closed: ' || $host)};</pre>
The following parameters are available:
! Name
! Description
|- valign="top"
| <code>host</code>
| The host of the request URI.
|- valign="top"
| <code>http-version</code>
| The HTTP version used for the request.
|- valign="top"
| <code>is-secure</code>
| Indicates if the connection is secure.
|- valign="top"
| <code>origin</code>
|- valign="top"
| <code>protocol-version</code>
| The version of the used protocol (max. 1.3).
|- valign="top"
| <code>query-string</code>
| The query string of the request URI.
|- valign="top"
| <code>isrequest-secure</code>| Indicates if the connection is secure.|- valign="top"| <code>is-secureuri</code>
| The Request URI to use for this request.
|- valign="top"
| <code>hostsub-protocols</code>| The host List of the request URI.|- valign="top"| <code>sec-websocketconfigured sub-version</code>| The websocket versionprotocols.
|}
General information on the request can be retrieved via the [[Request Module]]. =TippsWriting Applications= The [[WebSocket Module]] contains functions for interacting with other clients or manage specific clients. For example, you can store and access client-specific properties for a WebSocket connection or close the connection of clients. Note that one WebSocket connection can be opened per browser tab. In contrast, only one HTTP session exists for multiple tabs in in a browser. If you want to keep client-specific data on the web server, you can either store them in HTTP sessions or in the WebSocket connection. Note further that the results of functions annotated with <code>%ws:close</code> or <code>%ws:error</code> will not be transmitted to the client. Both annotations have rather been designed to gracefully close connections, write log data, remove clients from session data, etc. For keeping the connection alive it is recommendable to use heart-beats, and send regular pings to the server. There is no ideal timespan for sending pings: It should not be sent too often, but you should also consider possible network latencies. If your HTTP connection is secure, you should use the <code>wss</code> instead of the <code>ws</code> scheme.
=Examples= ==Basic Example==
The following chapter explains how to create a simple basic web application with WebSockets. You can find another example in the BaseX source code.
</pre>
The <code>send</code> function can be called to pass on a string to the server. There are no heart-beats in this example. This means that the connection is terminated if nothing happens for 5 minutes (estandard timeout). gIt will also be closed if you send a message that exceeds the standard text size. ==Chat Application== In the full distributions of BaseX, you will find a little self-contained chat message) to the serverapplication that demonstrates how WebSockets can be used in practice. =Changelog=
