A native, RFC 6455 WebSocket implementation for Delphi and C++Builder. Build clients and servers that hold thousands of concurrent connections, run on Windows, macOS, Linux, iOS and Android, and survive flaky networks with the built-in WatchDog auto-reconnect.
A drop-in VCL/FMX component that turns the WebSocket protocol into a property-and-event API native Delphi developers recognise.
A Delphi WebSocket component is a non-visual component you drop on a form (or instantiate at runtime) to open a full-duplex TCP channel between a Delphi application and any RFC 6455 WebSocket peer — a browser, a Node.js service, an nginx reverse proxy, a Mosquitto broker, an OpenAI Realtime endpoint or another Delphi process. Unlike polling HTTP, a WebSocket keeps the connection open: the server can push data the moment it is available, with millisecond latency and no per-message HTTP overhead.
sgcWebSockets has been the reference WebSocket library in the Delphi ecosystem since 2013. The same TsgcWebSocketClient and TsgcWebSocketHTTPServer components run unchanged on Delphi 7 through Delphi 13, on Win32, Win64, Linux64, macOS, iOS and Android, and on C++Builder C2007 through C13. There is no managed runtime, no .NET interop layer, no JavaScript bridge — it is a pure Pascal implementation that compiles into your binary.
Writing one PING/PONG handler is easy. Surviving a TLS-terminating reverse proxy, an IIS WebSocket module, a corporate firewall, a mobile cellular handover and a 5,000-client load test is not.
Plain WebSocket (ws://), TLS WebSocket (wss://), WebSocket over HTTP/2, WebSocket over QUIC/HTTP/3, raw TCP fallback — same component, same events. Switch transport by changing one property.
Enable WatchDog and the client will reconnect with exponential back-off, re-authenticate, re-subscribe to MQTT topics and replay any queued publications — the canonical mobile / IoT pattern, already written.
The server uses an IOCP / kqueue / epoll reactor under the hood. You write event handlers; the library schedules them across a thread pool with per-connection serialisation.
Negotiated automatically per RFC 7692. Cuts JSON payloads by 70–90 % and is supported by every modern browser and load balancer.
MQTT 3.1.1/5.0, AMQP 0.9.1/1.0, STOMP, WAMP and Server-Sent Events ride on top of the same WebSocket transport — one TCP socket, multiple application protocols.
TsgcWebSocketHTTPServer serves static files, REST endpoints, JWT- and OAuth2-protected resources, gzip-compressed responses and HTTP/2 upgrade in the same process as your WebSocket endpoint.
OpenSSL (cross-platform), SChannel (Windows kernel TLS) or HTTP.sys. Client certificates, SNI, ALPN, TLS 1.3 with 0-RTT.
Server-side Channels group connections by name. Broadcast, BroadcastByChannel and BroadcastByUser fan out to thousands of peers in a single call.
In production at banks, exchanges, IoT fleets and trading firms since 2013. Updated every month; history.txt tracks every fix.
Everything the RFC says, plus the operational hardening real deployments need.
| Capability | Client | Server |
|---|---|---|
| RFC 6455 framing (text, binary, ping, pong, close) | Yes | Yes |
| permessage-deflate (RFC 7692) | Yes | Yes |
| Fragmented & continuation frames | Yes | Yes |
| Masked client messages | Yes | n/a |
| TLS 1.2 / 1.3 (OpenSSL + SChannel) | Yes | Yes |
| Client certificates / mTLS | Yes | Yes |
| JWT & OAuth2 authentication | Yes | Yes |
| HTTP/2 + WebSocket (RFC 8441) | Yes | Yes |
| HTTP/3 + WebSocket over QUIC (RFC 9220) | Yes | Yes |
| WatchDog auto-reconnect | Yes | n/a |
| Heart-beat (PING/PONG) | Yes | Yes |
| Channels & broadcast | n/a | Yes |
| Sub-protocols (MQTT / AMQP / STOMP / WAMP / SSE) | Yes | Yes |
| HTTP.sys hosting (Windows kernel) | n/a | Yes |
| Linux daemon mode | Yes | Yes |
Drop a TsgcWebSocketClient on the form, set Host / Port, handle OnMessage, set Active := True.
uses
sgcWebSocket, sgcWebSocket_Classes;
procedure TForm1.FormCreate(Sender: TObject);
begin
WS := TsgcWebSocketClient.Create(nil);
WS.URL := 'wss://echo.websocket.events';
WS.WatchDog.Enabled := True;
WS.WatchDog.Interval := 5;
WS.OnConnect := WSConnect;
WS.OnMessage := WSMessage;
WS.OnDisconnect := WSDisconnect;
WS.Active := True;
end;
procedure TForm1.WSMessage(Connection: TsgcWSConnection; const Text: string);
begin
Memo1.Lines.Add('<< ' + Text);
end;
procedure TForm1.ButtonSendClick(Sender: TObject);
begin
WS.WriteData('{"hello":"world"}');
end;Server side is symmetric — drop a TsgcWebSocketHTTPServer, set Port, handle OnConnect and OnMessage, call Broadcast to fan out to every connected peer.
One source tree, 22 runtime packages — covering every Delphi release still in active commercial use.
| Edition | Versions |
|---|---|
| Delphi / RAD Studio | 7, 2007, 2009, 2010, XE, XE2, XE3, XE4, XE5, XE6, XE7, XE8, 10 Seattle, 10.1 Berlin, 10.2 Tokyo, 10.3 Rio, 10.4 Sydney, 11 Alexandria, 12 Athens, 13 |
| C++Builder | 2007, 2009, 2010, XE, XE2, XE3, XE4, XE5, XE6, XE7, XE8, 10, 10.1, 10.2, 10.3, 10.4, 11, 12, 13 |
| FreePascal / Lazarus | 3.x (via sgcIndy base) |
| Platforms | Win32, Win64, Linux64, macOS Intel/ARM, iOS device + simulator, Android ARM/ARM64 |
The WebSocket transport is the foundation of every other protocol in the library.
Background on the RFC 6455 protocol, the handshake, framing and use cases.
Run MQTT 3.1.1 / 5.0 over the same WebSocket connection.
Multiplexed HTTP/2 with server push and WebSocket-over-HTTP/2.
WebSocket vs SSE vs HTTP/2 push vs MQTT vs WebRTC — decision matrix.
Pattern guide for broadcasting to subsets of connections.
How the auto-reconnect lifecycle works under the hood.
Tuning permessage-deflate for throughput vs CPU.
Every commercial Delphi release from Delphi 7 (2002) through Delphi 13 (2025), plus matching C++Builder versions. We ship 22 separate runtime packages — one per IDE — from a single source tree. There is no separate “legacy” SKU; every customer gets every version.
Yes. Set URL := 'wss://...' and pick a TLS provider: OpenSSL (cross-platform, ships with the trial), SChannel (Windows kernel TLS, no DLLs to deploy), or HTTP.sys (server-side, certificate stored in the Windows certificate store). Client certificates, SNI, ALPN, TLS 1.3 and 0-RTT are all supported.
On Windows the server uses IOCP and routinely scales to 50,000+ concurrent connections per process on commodity hardware. On Linux the epoll reactor scales similarly. The hard limit is OS-level (file descriptors, ephemeral port range, kernel memory), not the library.
Royalty-free per-developer perpetual licence with one year of updates included. Single-developer, team and site licences available — see pricing. Source code is included with every commercial edition.