Codename One - Can't read from socket on real device

Question

I'm developing an iOS app, using Codename One. I extended the SocketConnection class, in order to receive data from a server.

class CustomSocketConnection extends SocketConnection {

    private OutputStream os;
    private InputStream is;
    private InputStreamReader isr;
    private String rawMessage;

    public CustomSocketConnection(){
        os = null;
        is = null;
        isr = null;
        rawMessage = null;
    }

    public synchronized String getRawMessage(){
        return rawMessage;
    }

    @Override
    public void connectionError(int errorCode, String message) {
        rawMessage = null;
        ToastBar.showErrorMessage("Error Connecting. ErrorCode: " + errorCode + " Message: " + message);
        System.out.println(">>>CustomSocketConnection, connectionError. Error Connecting. ErrorCode: " + errorCode + " Message: " + message);
    }

    @Override
    public void connectionEstablished(InputStream is, OutputStream os) {
        System.out.println(">>>CustomSocketConnection, connectionEstablished");

        char termination = '\n';

        int length = 1024;
        char[] buffer = new char[length];
        byte[] bufferByte = new byte[length];
        StringBuilder stringBuilder = new StringBuilder();
        System.out.println(">>>CustomSocketConnection, connectionEstablished, prima del while");

        try {
            InputStreamReader isr = new InputStreamReader(is, "UTF-8");
            System.out.println(">>>CustomSocketConnection, connectionEstablished, prima della read");

            while(true){
                System.out.println(">>>CustomSocketConnection, loop di read, inizio");
                int read = isr.read();
                System.out.println(">>>CustomSocketConnection, loop di read, subito dopo la read");
                char c = (char) read;
                if (read == -1) rawMessage = null;

                System.out.println(">>>CustomSocketConnection, loop di read, letto: " + c);

                while(c != termination){
                    stringBuilder.append(c);
                    read = isr.read();
                    c = (char) read;
                    if (read == -1) rawMessage = null;
                }
                rawMessage = stringBuilder.toString();
                if(rawMessage != null) doActions(rawMessage);

                //System.out.println(">>>CustomSocketConnection, connectionEstablished, ho letto: " + rawMessage + "FINE");
            }


        } 
        catch (IOException ex) {
            System.out.println(">>>CustomSocketConnection, connectionEstablished, errore: " + ex.getMessage());
        }

        System.out.println(">>>CustomSocketConnection, connectionEstablished, dopo il while"); 

    }

    private void doActions(String msg){
        //do something

    }
}

In the connectionEstablished method, I read data from server, using the read method of the InputStreamReader class.

If I run the app on the simulator, it works properly and it receives data from server. When I launch the app on real devices (iPad mini, 32-bit device, iOS version 8.1.1 12B435, more details here; iPhone 7s, 64-bit device, iOS version 11.2.5 15D60), the read method doesn't receive data from server. In fact, I can see the string printed by the println before the read method, but I can't see the string printed by the println after the read method.

The issue is not server-side, because I developed an Android app and it receive data from the same server. There aren't firewall restrictions or other network limitations: Android app and the Codename One simulator both receive data when connected on the same local network of the server or from another one.

What's wrong?

Is your device in same network ? Seems to be something related to network, wifi, etc — GIJOW, Jan 22 '18 at 13:46
What URL and port are you using? Maybe the firewall on your development machine is blocking external communication? — Shai Almog, Jan 23 '18 at 05:24
I'm using a public IP address and the port 8888. I connected the pc running the simulator and the iPad to the same network: the simulator reads data, the iPad doesn't receive data. — A M, Jan 23 '18 at 07:28
Where is this stuck exactly? Is it stuck during lookup or is nothing happening at all. I noticed you used `System.out` instead of `Log.p()` which would allow you to review the logs after the fact. Using a network monitor tool to inspect the traffic going to the server would also help in pinpointing the issue. — Shai Almog, Jan 23 '18 at 08:40
@ShaiAlmog In device logs, I can see the string printed by the System.out.println() before the read method, but I can't see that afted the read method. Moreover. I used Microsoft Network Monitor to inspect the traffic on the server machine. It correctly sends data in both cases (on simulator and on device). Any suggestions? — A M, Jun 11 '18 at 15:12
Did you flush the written data in the server? If you write more than one byte does it change the results? Can you produce a standalone test case that reproduces this? — Shai Almog, Jun 12 '18 at 04:16
@ShaiAlmog Yes, I flush data. I wrote more than one byte, but nothing changes. About test, what kind of test do you mean? — A M, Jun 12 '18 at 08:11

score 1 · Accepted Answer · answered Jun 12 '18 at 17:06

Solved using InputStream instead of InputStreamReader.

@Override
public void connectionEstablished(InputStream is, OutputStream os) {
    System.out.println(">>>CustomSocketConnection, connectionEstablished");

    char termination = '\n';

    StringBuilder stringBuilder = new StringBuilder();
    System.out.println(">>>CustomSocketConnection, connectionEstablished, prima del while");

    try {
        System.out.println(">>>CustomSocketConnection, connectionEstablished, prima della read");

        while(true){
            System.out.println(">>>CustomSocketConnection, loop di read, inizio");
            int read = is.read();
            System.out.println(">>>CustomSocketConnection, loop di read, subito dopo la read");
            char c = (char) read;
            if (read == -1) rawMessage = null;

            System.out.println(">>>CustomSocketConnection, loop di read, letto: " + c);

            while(c != termination){
                stringBuilder.append(c);
                read = is.read();
                c = (char) read;
                if (read == -1) rawMessage = null;
            }
            rawMessage = stringBuilder.toString();
            if(rawMessage != null) doActions(rawMessage);

            //System.out.println(">>>CustomSocketConnection, connectionEstablished, ho letto: " + rawMessage + "FINE");
        }


    } 
    catch (IOException ex) {
        System.out.println(">>>CustomSocketConnection, connectionEstablished, errore: " + ex.getMessage());
    }

    System.out.println(">>>CustomSocketConnection, connectionEstablished, dopo il while"); 

}

Can anyone explain me why it's working with InputStream?

I missed that in your code. `InputStreamReader` translates a call to `read()` into a buffered call since it needs to convert bytes to chars. For that you usually need more than one. Furthermore, buffered reading is much faster. So when you write `read()` it translates to `read(arrayOf8192Bytes)`. — Shai Almog, Jun 13 '18 at 05:29

Codename One - Can't read from socket on real device

1 Answers1