Android read/write in same socket from ServerSocket

Question

I have an android app which will create a ServerSocket and accept a socket. I want it can communicate(read/write) with remote device.

My sample code like following:

mListenSocket = new ServerSocket();
mListenSocket.setReuseAddress(true);
mListenSocket.bind(new InetSocketAddress(DOCK_PORT));
mSocket = mListenSocket.accept();

Thread {
    loop {
    outputStream = mSyncSocket.getOutputStream();
    inputStream = mSyncSocket.getInputStream();
    ...
    inputStream.read(data)
    outputStream.write(data);
    ...
    }
}

It can read right inputStream data from client, but the second time read() always return -1 after I write data in outputStream firt time .

I have no idea about this issue. Somebody can give me some tips? Thanks a lot.

======================================================================

I think I need to express my problem more clearly.

There are two devices(A, B), and their workflow as follows:

Type 1 task:
1. A sends command to B
2. B receives command and reply message to A
3. A receives message, Done.

Type 2 task:
1. A sends command to B, Done.

Above tasks are asynchronized.

My old method was that create a ServerSocket on A and B device respectively to handle A->B and B->A communication.
I think maybe one socket can resolve above task, but one socket will encounter read -1 issue.
Someone can give me more advices? Thanks a lot.

Take the first two statements of the loop out of the loop. Put them before the loop. You should initiate those variables only once. — greenapps, Feb 04 '16 at 13:27
sorry for the late reply.'loop' is something like 'while', 'for' ...etc sample code omitted too much. I did initiate those variables before loop. — Derek Tsai, Feb 14 '16 at 16:12

user207421 · Answer 1 · 2016-02-05T09:26:08.180

0

read() returns -1 because the peer has closed the connection. You should do likewise, and stop reading, and stop handling the connection completely. It's finished.

edited Feb 05 '16 at 09:26

answered Feb 05 '16 at 08:43

user207421

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sorry for the late reply. I'm really appreciate your response. – Derek Tsai Feb 14 '16 at 16:19

score -1 · Answer 2 · edited May 23 '17 at 12:15

-1

I use something like this:

final DataOutputStream dos = new DataOutputStream(s.getOutputStream());   
final BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream(), "UTF-8"));

// Send the login data.
final JSONObject login = new JSONObject();

// Send the login message.
dos.write((login.toString() + "\r\n").getBytes());

// Wait until we receive something from the server.
String receivedMessage;
while ((receivedMessage = in.readLine()) != null) {
    Log.i(TAG, "Received data: " + receivedMessage);
    processMessagesFromServer(dos, receivedMessage);
}

I use a normal socket instead of ServerSocket. Please check this thread for more information.

edited May 23 '17 at 12:15

Community

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answered Feb 04 '16 at 13:06

Blehi

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Zero evidence here that the client is sending lines. The mixture of `DataOutputStream` and `BufferedInputStream`is bizarre. – user207421 Feb 06 '16 at 09:26
We always use the `\r\n` separator .. so for us it is working properly. Do you have better idea instead of the mixture of `DataOutputStream` and `BufferedInputStream`? Please share it with us. – Blehi Feb 08 '16 at 13:44
sorry for the late reply. I'm really appreciate your response. – Derek Tsai Feb 14 '16 at 16:18

Android read/write in same socket from ServerSocket

2 Answers2