WebSocket is a web technology providing for bi-directional, full-duplex communications channels, over a single Transmission Control Protocol (TCP) socket. The WebSocket API is being standardized by the W3C, and the WebSocket protocol has been standardized by the IETF as RFC 6455.
WebSocket is designed to be implemented in web browsers and web servers, but it can be used by any client or server application. The WebSocket protocol makes possible more interaction between a browser and a web site, facilitating live content and the creation of real-time games. This is made possible by providing a standardized way for the server to send content to the browser without being solicited by the client, and allowing for messages to be passed back and forth while keeping the connection open. In this way a two-way (bi-direction) ongoing conversation can take place between a browser and the server. A similar effect has been done in non-standardized ways using stop-gap technologies such as comet.
In addition, the communications are done over the regular TCP port number 80, which is of benefit for those environments which block non-standard Internet connections using a firewall. WebSocket protocol is currently supported in several browsers including Firefox and Google Chrome. WebSocket also requires web applications on the server to be able to support it.More Information
sgcWebSockets is a complete package providing access to WebSockets protocol, allowing to create WebSockets Servers, Intraweb Clients or WebSocket Clients in VCL, Lazarus/FPC and Firemonkey applications.
sgcWebSockets implements 3 different types of WebSocket authentication:
Client needs to do send an HTTP GET passing username and password, and if authenticated, server response a Session ID. With this Session ID, client open websocket connection passing as a parameter. You can use a normal HTTP request to get a session id using and passing user and password as parameters
example: (user=admin, password=1234) --> http://localhost/sgc/req/auth/session/admin/1234
This returns a token that is used to connect to server using WebSocket connections:
Client open websocket connection passing username and password as a parameter.
example: (user=admin, password=1234) --> http://localhost/sgc/auth/url/admin/1234
implements Basic Access Authentication, only applies to VCL Websockets (Server and Client) and HTTP Requests (client webbrowsers don't implement this type of authentication). When a client tries to connect, it sends a header using AUTH BASIC specification.
Every time a new WebSocket connection is established, sgcWebSockets creates a TsgcWSConnection class where you can access to some properties like identifier, bytes received/sent, client IP... and there is a property called Data where you can store objects in memory like database access, session objects...
SSL support is based on Indy implementation, so you need to deploy openssl libraries in order to use this feature. In Compiled Demos file, there is a directory called Third-Parties/ openssl, where you can find the libraries need for every Delphi Version.
This is a feature that works very well when you need to send a lot of data, usually using a binary message, because it compresses WebSocket message using protocol "PerMessage_Deflate" which is supported by some browsers like Chrome.
Usually Server have more than one IP, if you enable a WebSocket Server and set listening port to 80, when server starts, tries to listen port 80 of ALL IP, so if you have 3 IP, it will block port 80 of each IP's.
Bindings allows to define which exact IP and Port are used by the Server. Example, if you need to listen on port 80 for IP 127.0.0.1 (internal address) and 188.8.131.52 (public address).
SGC Default Protocol implements a QoS (Quality of Service) for message delivery, there are 3 different types:
where messages are delivered according to the best efforts of the underlying TCP/IP network. Message loss or duplication can occur. This level could be used, for example, with ambient sensor data where it does not matter if an individual reading is lost as the next one will be published soon after.
where messages are assured to arrive but duplicates may occur.
where message are assured to arrive exactly once. This level could be used, for example, with billing systems where duplicate or lost messages could lead to incorrect charges being applied.
SGC Default Protocol implements Queues to add persistence to published messages (it's only available for Published messages)
Messages are not queued on Server
only last message is queued on Server, and is sent every time a client subscribes to a new channel or connects to server.
All messages are queued on Server, and are sent every time a client subscribes to a new channel or connects to server.
sgcWebSockets SGC Protocol supports transactional messaging, when a client commits a transaction, all messages sent by client are processed on server side. There are 3 methods called by client
Creates a New Transaction on server side and all messages that are sent from client to server after this method, are queued on Server side, until client calls to Commit or Rollback
When a client calls to commit, all messages queued by server are processed.
When a client calls to RollBack, all messages queued by server are deleted and not processed on server side.
TsgcWebSocketHTTPServer is a component that allows to handle WebSocket and HTTP connections using the SAME port. Is very useful when you need to setup a server where only HTTP port is enabled (usually 80 port). This component supports all TsgcWeBSocketServer features and allows to serve HTML pages.
You can serve HTML pages statically, using DocumentRoot property, example: if you save test.html in directory "C:\inetpub\wwwroot", and you set DocumentRoot to "C:\inetpub\wwwroot". If a client tries to access to test.html, it will be served automatically, example:
Bandwidth Throttling is supported by Server and Client components, if enabled, can limit the amount of bits per second sent/received by socket. Indy uses a blocking method, so if a client is limiting its reading, unread data will be inside client socket and server will be blocked from writing new data to client. As much slower is client reading data, much slower is server writing new data.
SSE are not part of WebSockets, defines an API for opening an HTTP connection for receiving push notifications from a server.
SSEs are sent over traditional HTTP. That means they do not require a special protocol or server implementation to get working. In addition, Server-Sent Events have a variety of features that WebSockets lack by design such as automatic reconnection, event IDs, and the ability to send arbitrary events.
On Server components, automatically sends a ping to all active WebSocket connections every x seconds.
On Client components, automatically sends a ping to server every x seconds.
On Server components, automatically restart server after unexpected disconnection.
On Client components, automatically reconnect to server after unexpected disconnection.
Client WebSocket components support WebSocket connections through proxies
Web Browsers without WebSockets support, can use Flash to connect to WebSocket Server (example: Internet Explorer from version 6 to 9).
If Flash is not enabled, then tries to connect using Server-Sent Events + XHR.
Load Balancing allows to distribute work between several back-end servers, every time a new client request a connection, it connects to a load balancer server (which is connected to back-end servers) and returns a connection string with information about host, port... which is used by client to connect to a server. If you have for example 4 servers, with this method all servers will have, more or less, the same number of connections, and work load will be similar.
If a client want to send a message to all clients of all servers, just use broadcast method, and this message will be broadcast to all servers connected to Load Balancer Server.
Compiled *.dcu files provided with free version are using default Indy and Intraweb version. If you have upgraded any of these packets, probably it won't work or you need to buy full source code version Buy Now
WebSocket messages are processed using Intraweb Async Events
Download Free Version of our WebSockets Components for Delphi. These components are completely Free including Commercial use. If you need source code, you can buy a license and get 1 year of free updates, Buy Now
The AutobahnTestsuite provides a fully automated test suite to verify client and server implementations of The WebSocket Protocol for specification conformance and implementation robustness.
We have tested sgcWebSockets Server and Client Components using this test suite and here you can view the results.
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