Is socket support works correct?

[destitutus]

Language server answers nothing if --socket option used. Is implementation broken?

node -v
v6.11.2

Ways to repeat. Install Language server, for example npm install -g ocaml-language-server
Run it via command line ocaml-language-server --socket=3000
Connect via telnet to server

$ telnet
telnet> toggle crlf
Will send carriage returns as telnet <CR><LF>.
telnet> open localhost 3000
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Content-Length: 58

{"jsonrpc":"2.0","id":2,"method":"initialize","params":{}}

It replays nothing on correct request.
If I change line https://github.com/Microsoft/vscode-languageserver-node/blob/master/server/src/main.ts#L1460-L1464

to

let server = net.createServer(socket => {
                server.close();
                output.on('data', function (d) {
                        socket.write(d)
                })
                socket.on('data', function (d) {
                        input.write(d)
                })
            }).listen(port);

it replay with correct response

$ telnet
telnet> toggle crlf
Will send carriage returns as telnet <CR><LF>.
telnet> open localhost 3000
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Content-Length: 58

{"jsonrpc":"2.0","id":2,"method":"initialize","params":{}}
Content-Length: 152

{"jsonrpc":"2.0","id":0,"method":"window/showMessageRequest","params":{"type":2,"message":"Cannot find merlin binary at \"ocamlmerlin\".","actions":[]}}

Is it known issue?

[dbaeumer]

@aeschli can you please answer. You originally put that in.

[aeschli]

Sorry, I'm not really the node streams expert. So maybe this never worked?

[PavelSosin]

It looks like ALL LSP implementations based on this package have the same issue!

[rcjsuen]

I've tried connecting to the example server in the past and also got nowhere. Please see Microsoft/vscode-languageserver-node-example#37..

[AHaberl]

So will there be a fix for this?

[dbaeumer]

Fixed. Published as 3.5.0-next.1

Please note that socket connections are only supported when both the client and server run on the same machine.

[dbaeumer]

@AHaberl usually a PR helps as well :-)

[rcjsuen]

@dbaeumer I don't understand your fix. The code for creating a server socket uses Net's createConnection function which is used for creating a socket that connects to the specified port. The server should be listening for connections on the specified port.

https://github.com/Microsoft/vscode-languageserver-node/blob/d40191a5a430a4362d6c19610d800eb7f7a95959/jsonrpc/src/socketSupport.ts#L39-L45

The server will not start because it tries to connect to port 3000 instead of listening on port 3000.

[rcjsuen]

I have opened #260 with a proposed fix that corrects the original problem that was caused by the pipes reading and writing in the wrong direction.

[dbaeumer]

@rcjsuen I forgot to add some documentation on how this is supposed to work:

To avoid any timing or port issues the pipe and the sockets are owned by the client processes since it is already running. The server process simply connects to the pipe / socket. In node term the VS Code process calls createServer, then starts the server process, waits until the server process has connected to the pipe / socket and then signals that the connection has been established and messages can be send back and forth.

I will update the documentation to make this clear for users that implement a server in a different programming language.

[rcjsuen]

Thank you for your clarification, @dbaeumer. I see now that the client is supposed to listen for connections on the specified port and the language server should be started up to connect to the specified port.

I hope the following code will be of help to someone.

import * as net from "net"
import * as child_process from "child_process"

const server = net.createServer((socket) => {
    // close the server and don't accept anymore connections
    server.close();
    socket.on("data", (message) => {
        console.log(message.toString());
    });
    initialize(socket);
});
server.listen(3000, () => {
    // ask the language server to connect to port 3000 once the setup has completed
    child_process.spawn("node", [ "out/src/server.js", "--socket=3000" ]);
});

let messageId = 1;

function send(socket: net.Socket, method: string, params: object) {
    let message = {
        jsonrpc: "2.0",
        id: messageId++,
        method: method,
        params: params
    };
    let json = JSON.stringify(message) + "\n";
    let headers = "Content-Length: " + json.length + "\r\n\r\n";
    socket.write(headers, "ASCII");
    socket.write(json, "UTF-8");
}

function initialize(socket: net.Socket) {
    send(socket, "initialize", {
        rootPath: process.cwd(),
        processId: process.pid,
        capabilities: {
            /* ... */
            workspace: {

            }
        }
    });
}