Develop Reference

LuaSocket server don't accept clients

Im making a lua script running at my pc, and need to connect from my android.
So in the lua script I just put this:
local socket = require 'socket'
local server = socket.tcp()
print("createdserver")
server:bind('*',7070)
print("binded")
while 1 do
server:listen(32)
local client = server:accept()
-- make sure we don't block waiting for this client's line
client:settimeout(10)
-- receive the line
local line, err = client:receive()
-- if there was no error, send it back to the client
if not err then client:send(line .. "\n") end
-- done with client, close the object
client:close()
end
And at android I got a really simple socket connection:
public Connection(String ip, int _port) {
//inMessage = new NetworkMessage();
buffer = new byte[16394];
try {
serverAddres = InetAddress.getByName(ip);
socket = new Socket(serverAddres, _port);
socketOut = socket.getOutputStream();
} catch (IOException e) {
Log.e("Connect", e.getMessage());
}
}
At android it just stays at "new Socket" and dont connect.

Im not familiar with lua but my understanding is that you are writing a new line to the socket and you want to receive on the Android side.
Normally if that is the case you need to get the inputStream not the output one since you are waiting for results. Furthermore you need to indefinitely (or till some conditions are met) to listen to the input stream for data on a separate thread (a standard in):
while(true){
if (inputStreamReader().read() != -1){
// do you processing
}
}

My notebook was changing its IP address so I couldnt reach it from the android, already solved!

Socket EADDRINUSE (Address already in use)

I am doing socket programming. I took reference from below link:
http://examples.javacodegeeks.com/android/core/socket-core/android-socket-example/
Below is detail about my issue. I have created Android lib for this ServerThread (my project requirement), and this is used in test app.
Now test app connect to this through lib and do the process. First time it works perfectly fine, but if I closed and reopen it crashed with exception:
"EADDRINUSE (Address already in use)"
Also tried serverSocket.setReuseAddress(true) this but no luck.
My code:
public void run() {
Socket socket = null;
try {
serverSocket = new ServerSocket(SERVER_PORT);
serverSocket.setReuseAddress(true);
} catch (IOException e) {
Log.e(TAG, "exception1= " + e.getMessage());
}
while (!Thread.currentThread().isInterrupted()) {
try {
socket = serverSocket.accept();
Log.d(TAG, "server Connected.......!!!!");
communicationThread = new CommunicationThread(
socket);
commThread = new Thread(communicationThread);
commThread.start();
} catch (IOException e) {
Log.e(TAG, "exception 2=" + e.getMessage());
}
}
}
If I call serverSocket.close() I am getting exception 2 as server socket close. Communication thread is same as given in previous link.

You have to call setReuseAddress(true) before the socket is bound to the port. You are calling it after, because you are passing the port to the constructor, which will bind the socket immediately.
Try this instead:
serverSocket = new ServerSocket(); // <-- create an unbound socket first
serverSocket.setReuseAddress(true);
serverSocket.bind(new InetSocketAddress(SERVER_PORT)); // <-- now bind it

TCP (and probably some other) sockets can't reuse the same port for a period after closing. This is to prevent confusion if there's data on the network from an existing connection. You can override this behavior, but the default is to wait for a period of time before allowing reuse of the port.
The call to fix this is setReuseAddress(true) on the server socket. But I'm not sure if it needs to be called on the first socket or the second, or both.
Edit:
Here's a blog post describing the TCP socket TIME_WAIT state and why it exists: http://www.serverframework.com/asynchronousevents/2011/01/time-wait-and-its-design-implications-for-protocols-and-scalable-servers.html

While other answers pointed out the importance of setReuseAddress(true), another problem that could arise is to construct the ServerSocket twice and call bind with the same parameters. For example if you call twice the code run() of the question, serverSocket will be assigned to a new instance of the ServerSocket class, but the old one is still living until garbage collected. Now constructing with the port value as parameter equals to bind the ServerSocket object, and you are going to end up with two ServerSocket bound to the same address, which is forbidden hence the exception. So build your serverSocket with your chosen port only once!

Try to create the instance of SocketServer outside of the run() method.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState)
try {
// create a new instance of an unbound socket first
serverSocket = new ServerSocket();
} catch (IOException e) {
e.printStackTrace();
}
}

Reconnecting to an Android Socket in order to wait for Server

So I have TCP server in Windows that is programmed in C++ and a client in JAVA, Android 4.0.4.
In Android, I connect like this:
public boolean sendConnectRequest()
{
while (isSocketConnected == false)
{
try {
if(comSocket == null)
comSocket = new Socket("192.168.0.1",1531);
isSocketConnected = comSocket.isConnected();
if (isSocketConnected) {
out = comSocket.getOutputStream();
in = comSocket.getInputStream();
}
else
comSocket.close();
}
catch (IOException ex)
{
Log.e("TCP Error", ex.getLocalizedMessage());
}
}
return true;
}
I typically have no problems with this code on the first connection to the server.
When i disconnect from the server, I call this:
public void closeConnection() {
if (comSocket != null)
{
try {
comSocket.close();
isSocketConnected = false;
if (out != null)
out.close();
if (in != null)
out.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
So here is the problem... I hit the home button on the smartphone, which places the program in pause. I start the program again and it calls the resume function in activity, which in turn starts the process toward reconnection. The connection is attempted and i get no errors. However, my Windows server records no connection. In Windows, I know that I am still blocked at:
SOCKET connectionSocket = accept(tcpNetworkData->socket, (struct sockaddr*)&from, &fromlen);
I believe this is normal. When I am in debug mode on the Android side, I notice that it returns immediately from the line: comSocket = new Socket("192.168.0.1",1531); This should indicate to me that a connection is made.
If you follow me so far... I should also say that if I shut the server down, the client resets by closing the connection and opening a new one. This time the comSocket = new Socket("192.168.0.1",1531) does not block as it should and the execution keeps going. This is obviously wrong. I think it is a resource release problem but why? With Winsock you can solve this problem with this line of code:
int so_reuseaddr = TRUE;
setsockopt(networkData->socket, SOL_SOCKET, SO_REUSEADDR, (const char*)&so_reuseaddr,sizeof(so_reuseaddr));
Can you do something similar with Android or do you have to? Thank you for your help!

According to the javadoc the connection is established once you call the constructor.
Socket(InetAddress address, int port)
Creates a stream socket and connects it to the specified port number at the specified IP address.
When you press the home button, your app goes in background but it does not get killed immediately, so your comSocket might be not null when you get back to your application. In that case you are not calling the constructor again, thus you are not reconnecting to the server. What you should do is
if(comSocket == null){
comSocket = new Socket("192.168.0.1",1531);
}else{
comSocket.connect(new InetSocketAddress("192.168.0.1",1531));
}
(and please please place the curly brackets :-) )

Something to keep in mind is that the isConnected() method isn't very reliable for detecting when the remote side has closed the connection, (here is an example).
You have to figure this out by reading or writing on the associated Input/Output Streams.
Try using PrintWriter.checkError(), which will return true as soon as the client can no longer connect to the server.

Android Connection to WebSocket hang

In my Android project I implemented a Faye client. But, when I call SocketChannel.socket().connect(...), the connection hangs and the next line does not run. It is as if I don`t set the timeout, or disconnect for timeout.
Thread.currentThread().setName("WebSocketConnector");
try {
// "java.net.SocketException: Address family not supported by protocol"
System.setProperty("java.net.preferIPv6Addresses", "false");
mTransportChannel = SocketChannel.open();
// mTransportChannel.configureBlocking(false);
// the following will block until connection was established or
// an error occurred!
mTransportChannel.socket().connect(
new InetSocketAddress(mWsHost, mWsPort), mOptions.getSocketConnectTimeout());
Log.i(TAG, "Socket connected");
// before doing any data transfer on the socket, set socket
// options
mTransportChannel.socket().setSoTimeout(
mOptions.getSocketReceiveTimeout());
mTransportChannel.socket().setTcpNoDelay(
mOptions.getTcpNoDelay());
return null;
} catch (IOException e) {
Log.e(TAG, e.getMessage());
return e.getMessage();
}
If I did so:
mTransportChannel = SocketChannel.open();
mTransportChannel.configureBlocking(false);
mTransportChannel.connect(socketAddress);
SocketChannel .isConnected() return false
What is the problem I don't understand?

DNS resolution might be blocking even before the connect() call. Put new InetSocketAddress(mWsHost, mWsPort) on a separate line, and print out its results. Chances are you are stuck there.
If that's not the case, check if you can connect to the target host/port with telnet:
~$ telnet host port

This problem is resolved. My wifi connection didn`t have access to private resource. But how I have other problem with web socket. It is
Android socket read method return -1

Android Bluetooth Socket Connect Hangs

I am having an issue where when I call sock.connect() it just hangs indefinitely. There is no exception and no timeout.
try
{
Method m = dev.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
sock = (BluetoothSocket) m.invoke(dev, 1);
sock.connect();
Thread.sleep(100);
in = sock.getInputStream();
out = sock.getOutputStream();
}
catch(ConnectTimeoutException ex)
{
return false;
}
catch(IOException ex)
{
return false;
}
catch(Exception ex)
{
return false;
}
The reason is that another app is using the bluetooth device already. I am trying to make my connection fail and at least throw an exception or something to let me know the device is already in use by another app.
Any other suggestions to approaching this?
Thanks.

Why are you calling Thread.Sleep? BluetoothSocket.connect is a blocking call. This means that your Thread.Sleep will not be called until connect returns with either a successful connection or throws an exception.
Are you calling this in an activity? As this will hang your activity. You should have 3 threads to handle bluetooth, an accept thread, connect thread and a connected thread. Like in the BluetoothChat example here:
http://developer.android.com/resources/samples/BluetoothChat/index.html