I'm new to dart/flutter. I'm trying to use WebSocketChannel to connect to a websocket server.
Is there a way to detect when the connection with server is completed?
What I want to do is to send some messages the moment the connection with server is completed.
In javascript implementation this was something done like this:
exampleSocket.onopen = function (event) {
exampleSocket.send("Here's some text that the server is urgently awaiting!");
};
Is there an alternative on dart/flutter ? Is it possible to use it with WebSocketChannel
The WebSocket
class static method connect
returns a Future that resolve to a web socket when the connection is established.
If you want to send a message when the connection is up something like that should work:
import 'dart:io';
import 'package:web_socket_channel/io.dart';
WebSocket.connect("ws://a.b.c.d").then((ws) {
// create the stream channel
var channel = IOWebSocketChannel(ws);
channel.sink.add("hello");
})
The package web_socket_channel must be added to pubspec.yaml dependencies.
Related
i'm facing an issue with my socket client on next.js . i have created a context for providing my socket instance for all components in the application , the problem is that when i want to use the socket context on my component i am using the useeffect hook be called once the socket is changed and i will handle on message call ( like any tutorial i have seen on the web ) but with new message on the socket the useeffect is not called at all . for those who may think this is context issue i should say its not i have tested socket initiation on the component itslef and still useeffect not being called .
here is the way im using the socket instance :
export default function MyComp(props){
const cookies = new Cookies()
const token = cookies.get('token');
const socket = io(routes.socket_url, { path: '/socket',
transports: ['websocket'],
query:{
token,
user_id:'someuserid'
}
});
useEffect(() => {
console.log('socket changed');
console.log(socket);
console.log('socket changed');
},[socket])
}
i can actually see the connection on my devtools and also see the message in the network tab so it means we have a connection (also checked on server ) but the console.log() part is never called on new messages .
and here is my component using the context .
export default function MyComp(props){
const socket = useContext(SocketContext);
useEffect(() => {
console.log('socket changed');
console.log(socket);
console.log('socket changed');
},[socket])
}
the connection in this one is also available in the devtools and it gets the new message on networks tab but the logging is never called in useeffect .
thank you for any help .
guys i found the answer . i was using socket.io-client v 3.1.1 and i started testing other versions . for some strange reason
in version 3 socket instance is not receiving any messages though the connection is already stablished and i can see the messages coming in the networks tab .
anyways i changed version from 3 to 2.1.1 and its working like a charm .
I want to implement a VSCode extension that uses the Language Server Protocol, but I want the server component to be on an actual server (in the cloud), and not a part of the VSCode extension.
Can I set the client extension to connect to a server via websockets or HTTP?
Multiple ServerOptions are supported when you initialize a LanguageClient according to the signature of ServerOptions.
you can use the StreamInfo if you want to use a real remove server as your language server. Here is a sample code to connect to your server via WebSocket and initialize a LanguageClient.
const connection = connectToServer(hostname, path);
const client = new LanguageClient(
"docfxLanguageServer",
"Docfx Language Server",
() => Promise.resolve<StreamInfo>({
reader: connection,
writer: connection,
}),
{});
private connectToServer(hostname: string, path: string): Duplex {
const ws = new WebSocket(`ws://${hostname}/${path}`);
return WebSocket.createWebSocketStream(ws);
}
I am not sure if you can control the location of the language server, but there is another option. You do not need to implement the Language Server Protocol to, for example, provide parsing help. In that case you can implement your own convenient parsing service API (tailored to the nature of the language you want to support).
Within your extension you subscribe to workspace edit events using workspace.onDidChangeTextDocument
Re-start a 1sec timeout every time the file on-change event is raised
When the timeout expires without any further file modification, gather all relevant files and send them to your parsing server
In your extension, create a DiagnosticCollection using https://code.visualstudio.com/api/references/vscode-api#languages.createDiagnosticCollection and replace populate it with the warnings/errors/hints resulting from the parsing server in the cloud.
Subscribe to other workspace events, e.g. workspace.onDidOpenTextDocument or workspace.onDidCloseTextDocument in order to keep the DiagnosticCollection content relevant
My TCP server uses netty.The situation is: When a client connects to the server,I will save the client's ip in a global variable(such as a Map); When the client is disconnected,I will remove the IP from the map.
I used channelConnected() and channelDisconnected() method in SimpleChannelHandler.But my problem is ,some times the channelDisconnected() method cannot catch the event when I think the client is disconnected(maybe the computer closed,or the client process closed,or some other situations...) Can you give me some suggestions.
Just use DefaultChannelGroup which will automatically remove the Channel from it when it was closed.
Alternative you can register a ChannelFutureListener to the Channels close future to do the removal from your map.
Something like this:
channel.getCloseFuture().addListener(new ChannelFutureListener() {
public void operationCompleted(ChannelFuture f) {
map.remove(f.getChannel());
}
});
Because of shared hosting, my redis server on the target host does not run on a port, but on a very specific socket, which can be connected to via the socket file, only accessible to my user.
However, I have not found how I can specify connection via a socket in the node_redis and connect-redis packages, the ones I want to use.
Anyone know how to do it?
Update: My answer below is not really correct. It turns out that the solution in the issue I mention below actually still works. It's more of a coincidence, IMO, but you can do something like this, and it should work:
var redis = require('redis'),
client = redis.createClient('/tmp/redis.sock');
As you see from the code snippet below, this will get passed to net.createConnection which will connect to the unix socket /tmp/redis.sock.
Old answer:
There is a closed issue about this node_redis/issues/204. It seems, thought, that the underlying node.js net.createConnection API has since changed. It looks as though it would be a quite small fix in node_redis' exports.createClient function:
exports.createClient = function (port_arg, host_arg, options) {
var port = port_arg || default_port,
host = host_arg || default_host,
redis_client, net_client;
net_client = net.createConnection(port, host);
redis_client = new RedisClient(net_client, options);
redis_client.port = port;
redis_client.host = host;
return redis_client;
};
It seems as though net.createConnection will attempt to connect to a unix socket if it's called with one argument, that looks like a path. I suggest you implement a fix and send a pull request, since this seems like something worth supporting.
There is no longer a connect string...
var client = redis.createClient(9000); // Open a port on localhost
var client = redis.createClient('/tmp/redis.sock'); // Open a unix socket
var client = redis.createClient(9000, 'example.com');
This, and options are documented on the README.
I am working with a 3rd party device which opens a tcp port that only allows one connection at a time. If my app connects to the port, all other connections are denied.
I'd like to find an app that basically connects to this port, then allows others to connect to it on a different port.
Any data sent out of the device's port is then rebroadcast to any connected client.
I know how to write such an app, but it seems like it would be something someone else has already thought off and written it & shared, and I could avoid taking the time to write it.
basicaly code would be:
1) start a tcp socket server, binding to TO_PORT (clients connect to this)
2) connect as a client to DEVICE_IP:DEVICE_PORT
3) when data is read into a buffer from DEVICE_IP:DEVICE_PORT, the buffer content is resent to each connected client.
4) everything else that makes it a stable, working program.
This is for windows, and I'd prefer it not require a java install.
My google skills have failed me.
Anyone know of such an app?
Not a complete solution for you, but might be interesting, though
http://www.codeproject.com/KB/IP/serversocket.aspx
http://www.codeproject.com/KB/IP/UniversalTCPSocketClass.aspx
Guess I'll answer my own question.
I implemented the solution my self.
Key points to my solution:
A class named IPClient which wraps up a TcpClient instance, uses async model of calling TcpClient.BeginConnect, BeginRead, etc. It has a Timer used for reconnecting if it loses connection.
This is the class that connects to the device.
It's public interface would look something like this:
public class IPClient{
public event EventHandler<MyConnectedArgs> Connected;
public event EventHandler<MyDisconnectedArgs>Disconnected;
public event EventHandler<MyDataReceivedArgs> DataReceived;
public bool Connect(string address, int port){...}
public bool Disconnect() {...}
}
To open the port that would allow other clients to connect, I used this library: http://codeproject.com/KB/IP/BasicTcpServer.aspx and modified it a bit.
It's job was to open a port, accept connections, and do the following:
in the Connected handler, start the listening port
in the Disconnected handler, stop the listening port
in the DataReceived handler, broadcast the data to any connected clients.
I'll leave out the rest of the boring details, but say it wasn't "too hard", and eventually I just had to roll my own.
command line usage: myapp.exe remote_addr remote_port listen_port
psuedocode/main idea of my program main:
static int Main(string[] args){
//SetConsoleCtrlHandler(my callback re: ctrl+C,etc)
//get command line params
var ipClient = new IPClient();
var myprovider = MyTcpServiceProvider();
var server = new TcpServer(myProvider, listenPort);
ipClient.Connected += (sender, e) => server.Start();
ipClient.Disconnected += (sender,e) => server.Stop();
ipClient.DataReceived += (sender,e)=> provider.BroadcastToClients(e.Data);
ipClient.Connect(remoteAddress, remotePort);
//wait for Ctrl+C or program exit
//shutdown code,etc
return 0;
}