static ConcurrentDictionary<string, JoystickProcess> clientToDevice;
private Thread listenThread;

public MainForm()
{
    InitializeComponent();

    Network network = new Network(this);
    clientToDevice = new ConcurrentDictionary<string, JoystickProcess>();

    listenThread = new Thread(network.receive);

    // Start threads in background
    listenThread.IsBackground = true;
    listenThread.Start();
}

public JoystickProcess getClient(string client)
{
    if (clientList.InvokeRequired)
    {
        // Causes System.ObjectDisposedException
        return (JoystickProcess) Invoke(new Func<JoystickProcess>(() => getClient(client)));
    }
    else
    {
        JoystickProcess process;
        if (clientToDevice.TryGetValue(client, out process))
            return process;
        return null;
    }
}

public void receive()
{
    int port = 1608;
    UdpClient client = new UdpClient(port);
    IPEndPoint end = new IPEndPoint(IPAddress.Any, port);

    String addr;
    byte[] recv;
    JoystickProcess process;

    while (true)
    {
        // Wait for data to be received
        recv = client.Receive(ref end);

        addr = end.Address.ToString();

        if (ipList.Contains(addr))
        {
            // Causes System.ObjectDisposedException
            process = main.getClient(addr);

            if (process != null && process.getDevice() != -1)
            {
                Task.Run(() => process.updateDevice(recv));
            }
        }
        else
        {
            ipList.Add(addr);
            main.addClient(addr);
        }
    }
}