mbroadst / qwebsockets

QWebSockets is a pure Qt implementation of WebSockets - both client and server.

Introduction

QWebSockets is a pure Qt implementation of WebSockets - both client and server. It is implemented as a Qt source code module (.pri file), that can easily be embedded into existing Qt projects. It has no other dependencies that Qt.

Features

• Text and binary sockets
• Frame-based and message-based signals
• Works through proxies
• Strict Unicode checking

Restrictions

Non-characters (according Unicode Standard 6.2) are rejected by QWebSockets, even if the UTF-8 sequence is valid.

Rationale

The WebSocket specification is talking about Valid UTF-8 codes and sequences. Strictly speaking, UTF-xx encodings are reversible. That means, that the 66 non-character codes (including U+FFFE and U+FFFF), are valid UTF-8, and hence are perfectly acceptable within WebSocket text messages.
According to the Unicode standard, they SHOULD NOT be used in information interchange, but a recent corrigendum clarifies that non-characters CAN be exchanged.
However, non-characters are for internal use, and hence, they are implementation specific (e.g. non-characters can be used to carry meta-information). They have to be interpreted.
When used with QString, they are replaced with U+FFFD - REPLACEMENT CHARACTER, and rendered - non-standard - as a question mark (this is the QString rendering of the non-character U+FFFD: �). Browsers keep the control characters untouched (this is the browser rendering of the non-character U+FDD0: �).

With QWebSockets, text messages are just that: a collection of human-readable characters. Text messages never have to be interpreted to be rendered correctly. In case, you still want to do implementation specific trickery, use binary messages instead. Indeed, if non-characters were allowed in text messages, then every text message has to be parsed, character-per-character, to find out if it contains special control codes, or a protocol should be devised that indicates whether the message contains that kind of control codes. We keep it simple: text is text and nothing more.

Requirements

Qt 5.x

Usage

Include the .pri file into your Qt project

include (websocket.pri)

Compliance

QWebSockets is compliant with RFC6455 and has been tested with the Autobahn Testsuite.
Only tests with Unicode non-characters do not pass from the Autobahn Testsuite (see Restrictions).

Missing Features

• WSS protocol
• Extensions and sub-protocols

License

This code is licensed under LGPL v2.1.