Server doesn't receive messages

[ulzu]

class Server: OSCServerDelegate {
    let server = OSCServer(address: "localhost", port: 9999) // doesn't matter if I enter "localhost" or ""
    func didReceive(_ message: OSCMessage) {
        print("Received message: \(message)")
    }
    func didReceive(_ data: Data) {
        print("Received data: \(data)")
    }

    func didReceive(_ bundle: OSCBundle) {
        print("Received bundle: \(bundle)")
    }
}
let server = Server()
let client = OSCClient(address: "localhost", port: requestDestinationPort)
client.send(request) // receiver responds with message through localhost:9999

Server does not receive the message.
Here's some console.

Server init: localhost, 9999, running: true
Client init: localhost, 12002
Sent OSCMessage [Address</serialosc/list> String<localhost> Int<9999>]

External OSC monitor listening at localhost:9999 does receive the message.

Debugger:
yudpsocket.c:76

int len=(int)recvfrom(socket_fd, outdata, expted_len, 0, (struct sockaddr *)&cli_addr, &clilen);

execution drops out somehow