My solution. I used Epson TM series. I think the port is 9100 for default.
In Manifest add:
<uses-permission android:name="android.permission.INTERNET"/>
in the activity use a Thread otherwise u you can the android.os.NetworkOnMainThreadException error.
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
try {
Socket sock = new Socket("192.168.1.168", 9100);
PrintWriter oStream = new PrintWriter(sock.getOutputStream());
oStream.println("Hi, test from Android Device");
oStream.println("\n");
oStream.close();
sock.close();
} catch (UnknownHostException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
}});
If not enough, add in manifest these:
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />