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Benjamin Sergeant 2019-01-03 18:00:48 -08:00
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README.md
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@ -3,7 +3,7 @@
## Introduction
[*WebSocket*](https://en.wikipedia.org/wiki/WebSocket) is a computer communications protocol, providing full-duplex
communication channels over a single TCP connection. *IXWebSocket* is a C++ library for Websocket communication. The code is derived from [easywsclient](https://github.com/dhbaird/easywsclient) and from the [Satori C SDK](https://github.com/satori-com/satori-rtm-sdk-c). It has been tested on the following platforms.
communication channels over a single TCP connection. *IXWebSocket* is a C++ library for client and server Websocket communication. The code is derived from [easywsclient](https://github.com/dhbaird/easywsclient) and from the [Satori C SDK](https://github.com/satori-com/satori-rtm-sdk-c). It has been tested on the following platforms.
* macOS
* iOS
@ -15,7 +15,7 @@ communication channels over a single TCP connection. *IXWebSocket* is a C++ libr
The examples folder countains a simple chat program, using a node.js broadcast server.
Here is what the API looks like.
Here is what the client API looks like.
```
ix::WebSocket webSocket;
@ -50,10 +50,66 @@ webSocket.send("hello world");
webSocket.stop()
```
Here is what the server API looks like. Note that server support is very recent and subject to changes.
```
// Run a server on localhost at a given port.
// Bound host name, max connections and listen backlog can also be passed in as parameters.
ix::WebSocketServer server(port);
server.setOnConnectionCallback(
[&server](std::shared_ptr<ix::WebSocket> webSocket)
{
webSocket->setOnMessageCallback(
[webSocket, &server](ix::WebSocketMessageType messageType,
const std::string& str,
size_t wireSize,
const ix::WebSocketErrorInfo& error,
const ix::WebSocketOpenInfo& openInfo,
const ix::WebSocketCloseInfo& closeInfo)
{
if (messageType == ix::WebSocket_MessageType_Open)
{
std::cerr << "New connection" << std::endl;
std::cerr << "Uri: " << openInfo.uri << std::endl;
std::cerr << "Headers:" << std::endl;
for (auto it : openInfo.headers)
{
std::cerr << it.first << ": " << it.second << std::endl;
}
}
else if (messageType == ix::WebSocket_MessageType_Message)
{
// For an echo server, we just send back to the client whatever was received by the client
// All connected clients are available in an std::set. See the broadcast cpp example.
webSocket->send(str);
}
}
);
}
);
auto res = server.listen();
if (!res.first)
{
// Error handling
return 1;
}
// Run the server in the background. Server can be stoped by calling server.stop()
server.start();
// Block until server.stop() is called.
server.wait();
```
## Build
CMakefiles for the library and the examples are available. This library has few dependencies, so it is possible to just add the source files into your project.
There is a Dockerfile for running some code on Linux, and a unittest which can be executed by typing `make test`.
## Implementation details
### Per Message Deflate compression.
@ -76,6 +132,7 @@ If the remote end (server) breaks the connection, the code will try to perpetual
* There is no text support for sending data, only the binary protocol is supported. Sending json or text over the binary protocol works well.
* Automatic reconnection works at the TCP socket level, and will detect remote end disconnects. However, if the device/computer network become unreachable (by turning off wifi), it is quite hard to reliably and timely detect it at the socket level using `recv` and `send` error codes. [Here](https://stackoverflow.com/questions/14782143/linux-socket-how-to-detect-disconnected-network-in-a-client-program) is a good discussion on the subject. This behavior is consistent with other runtimes such as node.js. One way to detect a disconnected device with low level C code is to do a name resolution with DNS but this can be expensive. Mobile devices have good and reliable API to do that.
* The server code is using select to detect incoming data, and creates one OS thread per connection. This isn't as scalable as strategies using epoll or kqueue.
## Examples
@ -92,21 +149,38 @@ If the remote end (server) breaks the connection, the code will try to perpetual
Here's a simplistic diagram which explains how the code is structured in term of class/modules.
```
+-----------------------+
+-----------------------+ --- Public
| | Start the receiving Background thread. Auto reconnection. Simple websocket Ping.
| IXWebSocket | Interface used by C++ test clients. No IX dependencies.
| |
+-----------------------+
| |
| IXWebSocketServer | Run a server and give each connections its own WebSocket object.
| | Each connection is handled in a new OS thread.
| |
+-----------------------+ --- Private
| |
| IXWebSocketTransport | Low level websocket code, framing, managing raw socket. Adapted from easywsclient.
| |
+-----------------------+
| |
| IXWebSocketHandshake | Establish the connection between client and server.
| |
+-----------------------+
| |
| IXWebSocket | ws:// Unencrypted Socket handler
| IXWebSocketAppleSSL | wss:// TLS encrypted Socket AppleSSL handler. Used on iOS and macOS
| IXWebSocketOpenSSL | wss:// TLS encrypted Socket OpenSSL handler. Used on Android and Linux
| | Can be used on macOS too.
+-----------------------+
| |
| IXSocketConnect | Connect to the remote host (client).
| |
+-----------------------+
| |
| IXDNSLookup | Does DNS resolution asynchronously so that it can be interrupted.
| |
+-----------------------+
```
## API