Accessing ethernet port connected to android phone

Question

I am trying to build an app for modbus tcp/ip client on my android device. I've attached a USB to ethernet port converter and I'm trying to communicate through my laptop as a server. I'm not able to connect to the network with the error saying:

java.net.ConnectionException: failed to connect to /192.168.29.244 (port 502) from /::(port 0): connect failed: ENETUNREACH (network is unreachable)

I'm trying that by keeping the phone on Wifi and data off/airplane mode so as not to confuse it with Wifi signals.

It works flawlessly when my android device and laptop are on the same wireless network, but when attempting a wired connection with the laptop, it fails with the above-mentioned error. But when I tried a wired connection with the network switch on which I've my entire wifi internet, it worked.

Not able to figure out the problem.

Table

Thread t1 = new Thread(() -> {
                /* The important instances of the classes mentioned before */
                con = null; //the connection

                /* Variables for storing the parameters */
                int port = Integer.parseInt(etPort.getText().toString());

                String ip = etIP.getText().toString();
                try {
                    InetAddress addr = InetAddress.getByName(ip);//the slave's address

                    con = new TCPMasterConnection(addr);
                    con.setPort(port);
                    con.setTimeout(500);
                    Log.d("Connection parameters", "Timeout: " + con.getTimeout() + " Port: " + port);
                    con.connect();
                    runOnUiThread(() -> {
                        tv.setText("Connected!!!");
                        connect.setText("Disconnect");
                    });
                } catch (Exception e) {
                    e.printStackTrace();
                    Log.e("Error!", e.toString());
                    runOnUiThread(() -> {
                        tv.setText(e.toString());
                    });
                }
            });
            if (connect.getText().equals("Connect"))
                t1.start();
            else {
                Log.d("In diconnect", "Coonection closed!");
                con.close();
                connect.setText("Connect");
                tv.setText("Disconnected!!!");
            }

Please provide enough code so others can better understand or reproduce the problem. — Community, Mar 05 '23 at 14:13

score 0 · Accepted Answer · answered Mar 03 '23 at 13:52

0

I am not sure that I completely understand the question, but I do think that it has something to do with you connecting your phone directly to your laptop.

When you connect your phone to a network device, such as router or switch, it get's the IP address from the DHCP server, but when you connect it directly to your laptop, your phone simply doesn't have any IP address, unless you set up a static address, so it's not visible on the network.

answered Mar 03 '23 at 13:52

Lookyus

80
9

Thanks, seems like an good idea. But unfortunately, I'll be able to test it in the next week only! – Darshan Modi Mar 03 '23 at 16:36
Do you have USB C class connector(or micro USB for older android devices) in your adapter?or its USB is type A? I wanted my Xiaomi redmi note 7 (Android 9)as modbus client and my laptop as modbus server.I used QTS1081B usb to ethernet adapter and this is my big mistake.I didn't research enough befor for true adapter.I connected this adapter to my phone via a OTG connector.This adapter is not supported by android devices.I should provide a USB class C to ethernet adapter that can be connected to my phone directly without need to OTG connector.So tcp link gets established correctly. – R1349 Mar 03 '23 at 18:37
Lookyus answer works!!! – Darshan Modi Mar 09 '23 at 11:10

Accessing ethernet port connected to android phone

1 Answers1