473 lines
16 KiB
Markdown
473 lines
16 KiB
Markdown
# Examples
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The [*ws*](https://github.com/machinezone/IXWebSocket/tree/master/ws) folder countains many interactive programs for chat, [file transfers](https://github.com/machinezone/IXWebSocket/blob/master/ws/ws_send.cpp), [curl like](https://github.com/machinezone/IXWebSocket/blob/master/ws/ws_http_client.cpp) http clients, demonstrating client and server usage.
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## Windows note
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To use the network system on Windows, you need to initialize it once with *WSAStartup()* and clean it up with *WSACleanup()*. We have helpers for that which you can use, see below. This init would typically take place in your main function.
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```cpp
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#include <ixwebsocket/IXNetSystem.h>
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int main()
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{
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ix::initNetSystem();
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...
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ix::uninitNetSystem();
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return 0;
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}
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```
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## WebSocket client API
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```cpp
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#include <ixwebsocket/IXWebSocket.h>
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...
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// Our websocket object
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ix::WebSocket webSocket;
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std::string url("ws://localhost:8080/");
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webSocket.setUrl(url);
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// Optional heart beat, sent every 45 seconds when there is not any traffic
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// to make sure that load balancers do not kill an idle connection.
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webSocket.setPingInterval(45);
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// Per message deflate connection is enabled by default. You can tweak its parameters or disable it
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webSocket.disablePerMessageDeflate();
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// Setup a callback to be fired when a message or an event (open, close, error) is received
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webSocket.setOnMessageCallback([](const ix::WebSocketMessagePtr& msg)
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{
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if (msg->type == ix::WebSocketMessageType::Message)
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{
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std::cout << msg->str << std::endl;
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}
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}
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);
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// Now that our callback is setup, we can start our background thread and receive messages
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webSocket.start();
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// Send a message to the server (default to TEXT mode)
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webSocket.send("hello world");
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// The message can be sent in BINARY mode (useful if you send MsgPack data for example)
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webSocket.sendBinary("some serialized binary data");
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// ... finally ...
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// Stop the connection
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webSocket.stop()
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```
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### Sending messages
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`websocket.send("foo")` will send a message.
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If the connection was closed and sending failed, the return value will be set to false.
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### ReadyState
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`getReadyState()` returns the state of the connection. There are 4 possible states.
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1. ReadyState::Connecting - The connection is not yet open.
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2. ReadyState::Open - The connection is open and ready to communicate.
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3. ReadyState::Closing - The connection is in the process of closing.
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4. ReadyState::Closed - The connection is closed or could not be opened.
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### Open and Close notifications
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The onMessage event will be fired when the connection is opened or closed. This is similar to the [JavaScript browser API](https://developer.mozilla.org/en-US/docs/Web/API/WebSocket), which has `open` and `close` events notification that can be registered with the browser `addEventListener`.
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```cpp
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webSocket.setOnMessageCallback([](const ix::WebSocketMessagePtr& msg)
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{
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if (msg->type == ix::WebSocketMessageType::Open)
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{
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std::cout << "send greetings" << std::endl;
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// Headers can be inspected (pairs of string/string)
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std::cout << "Handshake Headers:" << std::endl;
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for (auto it : msg->headers)
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{
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std::cout << it.first << ": " << it.second << std::endl;
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}
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}
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else if (msg->type == ix::WebSocketMessageType::Close)
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{
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std::cout << "disconnected" << std::endl;
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// The server can send an explicit code and reason for closing.
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// This data can be accessed through the closeInfo object.
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std::cout << msg->closeInfo.code << std::endl;
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std::cout << msg->closeInfo.reason << std::endl;
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}
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}
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);
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```
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### Error notification
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A message will be fired when there is an error with the connection. The message type will be `ix::WebSocketMessageType::Error`. Multiple fields will be available on the event to describe the error.
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```cpp
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webSocket.setOnMessageCallback([](const ix::WebSocketMessagePtr& msg)
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{
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if (msg->type == ix::WebSocketMessageType::Error)
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{
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std::stringstream ss;
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ss << "Error: " << msg->errorInfo.reason << std::endl;
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ss << "#retries: " << msg->eventInfo.retries << std::endl;
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ss << "Wait time(ms): " << msg->eventInfo.wait_time << std::endl;
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ss << "HTTP Status: " << msg->eventInfo.http_status << std::endl;
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std::cout << ss.str() << std::endl;
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}
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}
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);
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```
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### start, stop
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1. `websocket.start()` connect to the remote server and starts the message receiving background thread.
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2. `websocket.stop()` disconnect from the remote server and closes the background thread.
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### Configuring the remote url
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The url can be set and queried after a websocket object has been created. You will have to call `stop` and `start` if you want to disconnect and connect to that new url.
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```cpp
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std::string url("wss://example.com");
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websocket.configure(url);
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```
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### Ping/Pong support
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Ping/pong messages are used to implement keep-alive. 2 message types exists to identify ping and pong messages. Note that when a ping message is received, a pong is instantly send back as requested by the WebSocket spec.
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```cpp
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webSocket.setOnMessageCallback([](const ix::WebSocketMessagePtr& msg)
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{
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if (msg->type == ix::WebSocketMessageType::Ping ||
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msg->type == ix::WebSocketMessageType::Pong)
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{
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std::cout << "pong data: " << msg->str << std::endl;
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}
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}
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);
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```
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A ping message can be sent to the server, with an optional data string.
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```cpp
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websocket.ping("ping data, optional (empty string is ok): limited to 125 bytes long");
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```
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### Heartbeat.
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You can configure an optional heart beat / keep-alive, sent every 45 seconds
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when there is no any traffic to make sure that load balancers do not kill an
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idle connection.
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```cpp
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webSocket.setPingInterval(45);
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```
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### Supply extra HTTP headers.
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You can set extra HTTP headers to be sent during the WebSocket handshake.
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```cpp
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WebSocketHttpHeaders headers;
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headers["foo"] = "bar";
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webSocket.setExtraHeaders(headers);
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```
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### Subprotocols
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You can specify subprotocols to be set during the WebSocket handshake. For more info you can refer to [this doc](https://hpbn.co/websocket/#subprotocol-negotiation).
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```cpp
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webSocket.addSubprotocol("appProtocol-v1");
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webSocket.addSubprotocol("appProtocol-v2");
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```
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The protocol that the server did accept is available in the open info `protocol` field.
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```cpp
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std::cout << "protocol: " << msg->openInfo.protocol << std::endl;
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```
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### Automatic reconnection
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Automatic reconnection kicks in when the connection is disconnected without the user consent. This feature is on by default and can be turned off.
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```cpp
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webSocket.enableAutomaticReconnection(); // turn on
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webSocket.disableAutomaticReconnection(); // turn off
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bool enabled = webSocket.isAutomaticReconnectionEnabled(); // query state
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```
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The technique to calculate wait time is called [exponential
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backoff](https://docs.aws.amazon.com/general/latest/gr/api-retries.html). Here
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are the default waiting times between attempts (from connecting with `ws connect ws://foo.com`)
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```
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> Connection error: Got bad status connecting to foo.com, status: 301, HTTP Status line: HTTP/1.1 301 Moved Permanently
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#retries: 1
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Wait time(ms): 100
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#retries: 2
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Wait time(ms): 200
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#retries: 3
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Wait time(ms): 400
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#retries: 4
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Wait time(ms): 800
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#retries: 5
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Wait time(ms): 1600
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#retries: 6
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Wait time(ms): 3200
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#retries: 7
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Wait time(ms): 6400
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#retries: 8
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Wait time(ms): 10000
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```
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The waiting time is capped by default at 10s between 2 attempts, but that value can be changed and queried.
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```cpp
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webSocket.setMaxWaitBetweenReconnectionRetries(5 * 1000); // 5000ms = 5s
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uint32_t m = webSocket.getMaxWaitBetweenReconnectionRetries();
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```
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## WebSocket server API
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```cpp
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#include <ixwebsocket/IXWebSocketServer.h>
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...
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// Run a server on localhost at a given port.
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// Bound host name, max connections and listen backlog can also be passed in as parameters.
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ix::WebSocketServer server(port);
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server.setOnConnectionCallback(
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[&server](std::shared_ptr<WebSocket> webSocket,
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std::shared_ptr<ConnectionState> connectionState)
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{
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webSocket->setOnMessageCallback(
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[webSocket, connectionState, &server](const ix::WebSocketMessagePtr msg)
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{
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if (msg->type == ix::WebSocketMessageType::Open)
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{
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std::cerr << "New connection" << std::endl;
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// A connection state object is available, and has a default id
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// You can subclass ConnectionState and pass an alternate factory
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// to override it. It is useful if you want to store custom
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// attributes per connection (authenticated bool flag, attributes, etc...)
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std::cerr << "id: " << connectionState->getId() << std::endl;
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// The uri the client did connect to.
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std::cerr << "Uri: " << msg->openInfo.uri << std::endl;
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std::cerr << "Headers:" << std::endl;
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for (auto it : msg->openInfo.headers)
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{
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std::cerr << it.first << ": " << it.second << std::endl;
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}
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}
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else if (msg->type == ix::WebSocketMessageType::Message)
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{
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// For an echo server, we just send back to the client whatever was received by the server
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// All connected clients are available in an std::set. See the broadcast cpp example.
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// Second parameter tells whether we are sending the message in binary or text mode.
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// Here we send it in the same mode as it was received.
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webSocket->send(msg->str, msg->binary);
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}
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}
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);
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}
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);
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auto res = server.listen();
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if (!res.first)
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{
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// Error handling
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return 1;
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}
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// Run the server in the background. Server can be stoped by calling server.stop()
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server.start();
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// Block until server.stop() is called.
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server.wait();
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```
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## HTTP client API
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```cpp
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#include <ixwebsocket/IXHttpClient.h>
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...
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//
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// Preparation
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//
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HttpClient httpClient;
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HttpRequestArgsPtr args = httpClient.createRequest();
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// Custom headers can be set
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WebSocketHttpHeaders headers;
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headers["Foo"] = "bar";
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args->extraHeaders = headers;
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// Timeout options
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args->connectTimeout = connectTimeout;
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args->transferTimeout = transferTimeout;
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// Redirect options
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args->followRedirects = followRedirects;
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args->maxRedirects = maxRedirects;
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// Misc
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args->compress = compress; // Enable gzip compression
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args->verbose = verbose;
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args->logger = [](const std::string& msg)
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{
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std::cout << msg;
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};
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//
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// Synchronous Request
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//
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HttpResponsePtr out;
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std::string url = "https://www.google.com";
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// HEAD request
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out = httpClient.head(url, args);
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// GET request
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out = httpClient.get(url, args);
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// POST request with parameters
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HttpParameters httpParameters;
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httpParameters["foo"] = "bar";
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out = httpClient.post(url, httpParameters, args);
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// POST request with a body
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out = httpClient.post(url, std::string("foo=bar"), args);
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//
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// Result
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//
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auto statusCode = response->statusCode; // Can be HttpErrorCode::Ok, HttpErrorCode::UrlMalformed, etc...
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auto errorCode = response->errorCode; // 200, 404, etc...
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auto responseHeaders = response->headers; // All the headers in a special case-insensitive unordered_map of (string, string)
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auto payload = response->payload; // All the bytes from the response as an std::string
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auto errorMsg = response->errorMsg; // Descriptive error message in case of failure
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auto uploadSize = response->uploadSize; // Byte count of uploaded data
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auto downloadSize = response->downloadSize; // Byte count of downloaded data
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//
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// Asynchronous Request
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//
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bool async = true;
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HttpClient httpClient(async);
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auto args = httpClient.createRequest(url, HttpClient::kGet);
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// Push the request to a queue,
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bool ok = httpClient.performRequest(args, [](const HttpResponsePtr& response)
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{
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// This callback execute in a background thread. Make sure you uses appropriate protection such as mutex
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auto statusCode = response->statusCode; // acess results
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}
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);
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// ok will be false if your httpClient is not async
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```
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See this [issue](https://github.com/machinezone/IXWebSocket/issues/209) for links about uploading files with HTTP multipart.
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## HTTP server API
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```cpp
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#include <ixwebsocket/IXHttpServer.h>
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ix::HttpServer server(port, hostname);
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auto res = server.listen();
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if (!res.first)
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{
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std::cerr << res.second << std::endl;
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return 1;
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}
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server.start();
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server.wait();
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```
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If you want to handle how requests are processed, implement the setOnConnectionCallback callback, which takes an HttpRequestPtr as input, and returns an HttpResponsePtr. You can look at HttpServer::setDefaultConnectionCallback for a slightly more advanced callback example.
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```cpp
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setOnConnectionCallback(
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[this](HttpRequestPtr request,
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std::shared_ptr<ConnectionState> /*connectionState*/) -> HttpResponsePtr
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{
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// Build a string for the response
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std::stringstream ss;
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ss << request->method
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<< " "
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<< request->uri;
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std::string content = ss.str();
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return std::make_shared<HttpResponse>(200, "OK",
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HttpErrorCode::Ok,
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WebSocketHttpHeaders(),
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content);
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}
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```
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## TLS support and configuration
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To leverage TLS features, the library must be compiled with the option `USE_TLS=1`.
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If you are using OpenSSL, try to be on a version higher than 1.1.x as there there are thread safety problems with 1.0.x.
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Then, secure sockets are automatically used when connecting to a `wss://*` url.
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Additional TLS options can be configured by passing a `ix::SocketTLSOptions` instance to the
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`setTLSOptions` on `ix::WebSocket` (or `ix::WebSocketServer` or `ix::HttpServer`)
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```cpp
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webSocket.setTLSOptions({
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.certFile = "path/to/cert/file.pem",
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.keyFile = "path/to/key/file.pem",
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.caFile = "path/to/trust/bundle/file.pem", // as a file, or in memory buffer in PEM format
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.tls = true // required in server mode
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});
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```
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Specifying `certFile` and `keyFile` configures the certificate that will be used to communicate with TLS peers.
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On a client, this is only necessary for connecting to servers that require a client certificate.
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On a server, this is necessary for TLS support.
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Specifying `caFile` configures the trusted roots bundle file (in PEM format) that will be used to verify peer certificates.
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- The special value of `SYSTEM` (the default) indicates that the system-configured trust bundle should be used; this is generally what you want when connecting to any publicly exposed API/server.
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- The special value of `NONE` can be used to disable peer verification; this is only recommended to rule out certificate verification when testing connectivity.
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- If the value contain the special value `-----BEGIN CERTIFICATE-----`, the value will be read from memory, and not from a file. This is convenient on platforms like Android where reading / writing to the file system can be challenging without proper permissions, or without knowing the location of a temp directory.
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For a client, specifying `caFile` can be used if connecting to a server that uses a self-signed cert, or when using a custom CA in an internal environment.
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For a server, specifying `caFile` implies that:
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1. You require clients to present a certificate
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1. It must be signed by one of the trusted roots in the file
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