Connecting a QWebSocket to a given IPv6 address (no URL)

Pippin

Hello,

How exactly should I connect a QWebSocket to a server that is not behind a particual URL (so no QUrl to open), but merely an IPv6 address?

Think of it this way. I run a Qt program, and as a result a QWebSocketServer is listening. A friend wants to connect their QWebSocket to my QWebSocketServer. I give him my IPv6 address. How exactly is he supposed to connect his QWebSocket at this point?

I feel like the answer is about using QWebSocket::open(const QNetworkRequest&) but how exactly do I set an IPv6 address in a QNetworkRequest?

JonB

@Pippin
I don't know, but does How to connect to a website that has only IPv6 addresses without a domain name? syntax [...] work for a QUrl for a QWebSocket?

piervalli

Ipv4 or IPv6 you need an ip 'ws:// {ip}:{port}' or if you need open ssl use 'wss://' you can use Qurl.

Pippin

Thanks guys!

Things are not doing well but I'm hopeful this will change soon. This is the relevant piece of code:

const auto path = "ws://[" + ip.toString() + "]:54321";
const auto url = QUrl(path);

socketToOnlineServer.open(url);

When I run this code, the IPv6 given is mine (I got it here) and my other application (on the same PC) is running a listening QWebSocketServer. The other relevant piece of code is:

server.listen(QHostAddress::Any, 54'321);

That server never gets to emit the newConnection signal somehow. Yes, I made sure to connect its newConnection signal to a slot of mine. My OS is Ubuntu LTS 24.04, and just to be sure, I deactivated my firewall by running:

sudo ufw disable

But unfortunately, that didn't change anything. My listening QWebSocketServer never gets to meet my connecting QWebSocket from the other application.

Would you see any reason why this didn't work?

Christian Ehrlicher

Why the brackets for the ip?

Pippin

@Christian-Ehrlicher From the link provided by @JonB

literal IPv6 addresses should be put inside square brackets

Christian Ehrlicher

I would go with https://doc.qt.io/qt-6/qhostinfo.html#from Name to see if you pass a valid ip

Pippin

@Christian-Ehrlicher Indeed I don't pass a valid IP...

auto info = QHostInfo::fromName(/* my Ipv6 address here */);
std::cout << info.errorString().toStdString() << std::endl;
std::cout << info.lookupId() << std::endl;

gives:

Unknown error
-1

I'm not sure what's wrong though. I'm just passing my regular IPv6 address, which I got from https://whatismyip.org/

Nothing changes if I provide my IPv4 address instead. I use Proton VPN but then again, nothing changes if I turn it off and edit the code with my real IPv6 address.

danish777

To connect a QWebSocket client to a server using an IPv6 address, your friend needs to format the address properly in a WebSocket-compatible URL. IPv6 addresses must be enclosed in square brackets. Here's an example:

QWebSocket socket;
QUrl url(QStringLiteral("ws://[2001:0db8:85a3::8a2e:0370:7334]:12345"));
socket.open(url);

The ws:// scheme is used for unencrypted WebSocket.

Use wss:// if the server uses SSL.

Replace 12345 with the port your QWebSocketServer is listening on.

If you're using

QWebSocket::open(const QNetworkRequest&)

, just wrap the QUrl like this:

QNetworkRequest request(QUrl(QStringLiteral("ws://[ipv6-address]:port")));
socket.open(request);

Also make sure:

Both client and server have proper IPv6 connectivity.

Firewall or router isn’t blocking the IPv6 port.

Let me know if you hit issues with specific address formats or port bindings.

GrecKo

@Pippin you most likely need to open a port on your internet router.

Pippin

It's all good now, thank you guys. I can send and receive messages with a QWebSocket and a QWebSocketServer in NonSecureMode. I was curious to see if everything would keep working if I set the QWebSocketServer to SecureMode, and change all request URLs to "wss://[ipv6]:port" on the client side, but the socket gets disconnected immediately.

I don't know anything about certificates and SSL configuration, so that's something I'll have to look up eventually.

SGaist

What did you do that made things work ? It might be helpful to other people :-)

Pippin

@SGaist said in Connecting a QWebSocket to a given IPv6 address (no URL):

What did you do that made things work ? It might be helpful to other people :-)

There were two things:

The QWebSocketServer was set to SecureMode, while on the client's side, the request URLs were all "ws://", so changing the QWebSocketServer to NonSecureMode helped a lot.
When the lookup of QHostInfo is successful, the lookupId of is set to -1, and the errorString is then "Unknown error". So there really was no problem with this to begin with!