I have connected a mobile Android device to a PC and trying to make a communication with it via Socket communication over TCP.I use the connect API to make the connection. My PC here acts as a client and the Android device as a server.
The connect passes the very first time but it fails when I try to reconnect, the error is 10061 - connection refused actively by host.
if(connect((SOCKET)sock,(struct sockaddr*)&addr,sizeof(addr)) == SOCKET_ERROR)
{
fprintf(stderr, "Error = %d",errno);
return;
}
This happens intermittently so the point of firewall blocking the particular port is ruled out, Also I read in some forums that this may be a issue with limited backlog, however I increased the backlog in the listen call on the server to 100 but still this issue persists.
if(listen(socket,100) == -1)
{
fprintf(stderr, "Error = %d",errno);
return;
}
Could someone throw some light on this?
Note: This occurs on a particular set of PC's and in others this doesnt occur at all. Is it dependent on any hardware configuration?
Related
Modern programming is turning more and more frustrating. Trying to do a simple socket test app on Flutter (tested on Android). Code is simple and self explanatory:
void Connect()
{
print("connecting...");
Socket.connect("localhost", 80).then((Socket sock) {
socket = sock;
socket?.listen(dataHandler,
onError: errorHandler,
onDone: doneHandler,
cancelOnError: false);
socket?.write("GET / HTTP/1.1");
}).catchError((Object e) {
print("Unable to connect: $e");
});
}
Code throws exception. Output:
I/flutter (15930): connecting...
I/flutter (15930): Unable to connect: SocketException: OS Error: Connection refused, errno = 111, address = localhost, port = 47244
The port is always different, why TF is that happening?
The port number in the error message is the local port and not the remote port. There are an issue about this problem here: https://github.com/dart-lang/sdk/issues/12693
In short, when connecting using TCP, you need two ports. One local which is open on your device and one remote which is the port open on the system you are trying to call. After a connection is established, the communication is going between this two port numbers.
So the error indicates that your server running on localhost:80 is refusing the connection from your application. The local port number in the error message can often just be ignored since it is not really relevant to debug most issues.
I'm using this to upload some file. It works if I in a local connection, but if I use a external connection, i get this message: 425 Can't open data connection. from the ftp server.
I use the org.apache.commons.net.ftp.FTPClient and org.apache.commons.net.ftp.FTPFile libs.
public static String gravaImagem(String photoFile) {
FTPClient mFtp = new FTPClient();
try {
mFtp.connect(FTPHOST, PORTA);
mFtp.login(USUARIO, SENHA);
mFtp.setFileTransferMode(FTPClient.BINARY_FILE_TYPE);
mFtp.setFileType(FTPClient.BINARY_FILE_TYPE);
String origem = Environment.getExternalStorageDirectory().getPath()+File.separator+"Pictures"+File.separator+"ImageSec"+File.separator+photoFile;
FileInputStream fis = new FileInputStream(origem);
mFtp.storeFile(photoFile, fis);
mFtp.logout();
mFtp.disconnect();
} catch (SocketException e) {
e.printStackTrace();
return "Fail. (ERR#CON3)";
} catch (IOException e) {
e.printStackTrace();
return "Fail. (ERR#CON4)";
}
return "Imagem enviada ao servidor.";
}
Debug shows no exceptions.
From the internet:
First - the most common solution: change the active/passive mode
settings. But that might not work, and if it does its only a band-aid
covering up the real problem.
As I've mentioned in the past, one of the most common reasons that
this error occurs is a misconfiguration of the FTP server software
itself, related to SSL connections and firewalls, in which the
connection tries to establish itself on a bogus ip address. Read more
about FTP SSL through a NAT firewall here, some potential solutions
are included.
There are other less likely causes, such as:
The server is configured to always use the same port for passive mode connections, or the client is configured to always use the
same port for active mode connections, although in this case
usually the software in question should raise a different error
first, but I've seen this happen.
In passive mode, the firewall in front of the FTP server doesn't have the correct ports open. So the server tells the client to
connect to ipaddress 1.2.3.4 on port x, but the firewall doesn't
allow incoming connections on port x. Most firewalls are smart
enough to open up the port when it sees the PASV response. Vice
versa for active mode and the firewall in front of the FTP client.
From me:
I've used this library on andoird and it worked well, so see my copy/paste section.
I've worked before with Kryonet doing 1-to-1 communication and it worked nicely.
Now I'm doing a more 'standard' project where we'll have 1 server and several clients to connect to it.
The issue I'm having is as described in the title: client 1 connects, no problem. Then I ask for client 2 to connect and immediately client 1 disconnects. Somehow the server doesn't want to keep more than one simultaneous connection.
A couple of times we managed to have 2 connected and then whenever the 3rd connects the other drops.
Running on several different devices all ICS+ (galaxy nexus, tab2, SGS3).
The codes I'm using are very much like the examples:
server side:
server = new Server();
ServiceData.RegisterKryo(server.getKryo());
server.addListener(new MyServerListener());
try {
server.bind(ServiceData.SERVER_PORT_TCP);
server.start();
} catch (IOException e) {
Log.e(TAG, "IOException. Failed to start server. " + e.getMessage());
MyServer.this.stopSelf();
}
And then client side:
final String ip = intent.getExtras().getString(KEY_SERVER_IP);
listener = new MyClientListener();
client = new Client();
client.start();
ServiceData.RegisterKryo(client.getKryo());
client.addListener(listener);
try {
client.connect(5000, ip, ServiceData.SERVER_PORT_TCP);
} catch (IOException e) {
Log.e(TAG, "IOException. Failed to start client. " + e.getMessage() + "\n");
e.printStackTrace();
MyClient.this.stopSelf();
}
the listeners at the moment are just Log.v(TAG, "something happened); and I've also enabled all the logs from the Kryonet library with com.esotericsoftware.minlog.Log.set(com.esotericsoftware.minlog.Log.LEVEL_TRACE); so I can see when it's connecting and when it's disconnecting.
I receive two different messages upon disconnection:
DEBUG: [kryonet] Connection 3 timed out.
and
DEBUG: [kryonet] Unable to read TCP from:
really not sure what's on here and any help will be appreciated.
edit:
a bit more info:
I've realised that between INFO: [kryonet] Connection 3 connected: /192.168.0.104 and my listener receive the connected callback, it's taking around 9 seconds! Very odd.
To whom might get into the same issue.
Apparently it's an Android limitation (probably imposed because it's a mobile device)
I just moved the Server code to a normal Java application .jar and let the Android clients connect to the PC and it all works fine now. Until now tested with 6 devices connected with no problems.
I use this code
luugiathuy.com/2011/02/android-java-bluetooth/
The server side is the PC
the client is the device, with the app based on bluetooth chat example
The device (galaxy tab 7.0) can establish connection with the PC.
However the PC server (written in java and bluecove) did nothing, as nothing is connected.
The loop for trying to find connected device is
while(true) {
try {
System.out.println("waiting for connection...");
connection = notifier.acceptAndOpen();
Thread processThread = new Thread(new ProcessConnectionThread(connection));
processThread.start();
} catch (Exception e) {
e.printStackTrace();
return;
}
Output on PC:
uuid: 0000110100001000800000805f9b34fb
waiting for connection...
EDIT: source downloadhttps://github.com/luugiathuy/Remote-Bluetooth-Android
Same issue I got when I was trying in linux. But the reason (still not sure) when you run the bluetooth android application without turning on the Java server using bluecove, It will try to connect with the already installed bluetooth software. You may see the bluetooth icon asking for granting access to the mobile device.
To solve this, I just changed the uuid in the server and application (say from 1103 to 1101 and vice versa) and then started the server first and then the android application. Java server part started listening.
The reason I think may be the uuid when it did not found the bluecove stack service server, it got connected to the device server listening on same uuid. So after changing the uuid and making sure that the server is running before launching the android application should solve the issue.
If you are getting connected to the bluetooth system application and not to the Java bluecove server,
1) First change the uuid both server and android application.
2) Second make sure your server is running and listening on same uuid.
3) Launch the android application which try to communicate on same rfcomm connection uuid.
Server part code I took from : http://www.jsr82.com/jsr-82-sample-spp-server-and-client/
Library : http://code.google.com/p/bluecove/downloads/list
Yes, it happens with me too, I suggest you to fire following commend on shell, when it shows waiting for connection.
hcitool cc 58:C3:8B:D7:FA:F4
here 58:C3:8B:D7:FA:F4 is my device's bluetooth address, which should be replaced by your device's bluetooth address.
To get your device's bluetooth address, just start bluetooth in your device with discoverable mode and execute hcitool scan command, it will display all the active device with their name and bluetooth address.
Well you may run the above hcitool cc 58:C3:8B:D7:FA:F4 command via Java code as follows,
try
{
Process p=Runtime.getRuntime().exec("hcitool cc 58:C3:8B:D7:FA:F4");
}
catch ( Exception e )
{
}
The output from your program says it listens on UUID 0x1101. Is that true? The sample you reference shows it listening on a different UUID. Its Service Class Id is 0x04c6093b and is set as follows:
34 UUID uuid = new UUID(80087355); // "04c6093b-0000-1000-8000-00805f9b34fb"
35 String url = "btspp://localhost:" + uuid.toString() + ";name=RemoteBluetooth";
36 notifier = (StreamConnectionNotifier)Connector.open(url);
The two need to match on client and server.
I have been playing around with the bluetooth API for Android 2.2 (API level 8, HTC Desire) and had an app connecting to an embedded Bluetooth device using:
device.createRfcommSocketToServiceRecord(DEV_UUID);
This generated a pairing request as expected, however to streamline the connection process I wanted to avoid the user interaction when pairing so moved to API level 10 (HTC Desire with CyanogenMod 7) so I could use:
device.createInsecureRfcommSocketToServiceRecord(DEV_UUID);
When testing this also works as expected (connecting without prompting the user to pair), however when I try to create the secure RfcommSocket under API level 10 as before with 2.2 I get a connection refused exception...
java.io.IOException: Connection refused
at android.bluetooth.BluetoothSocket.connectNative(Native Method)
at android.bluetooth.BluetoothSocket.connect(BluetoothSocket.java:204)
As far as I can tell this should still work in the same way, prompting the user to pair?
EDIT:
Just tried again using the following code and the outcome is the same (working for insecure but not for secure), I will try and get my hands on a stock 2.3 device to test on.
try {
Method m = dev.getClass().getMethod("createInsecureRfcommSocketToServiceRecord", new Class[] { UUID.class } );
BluetoothSocket bs = (BluetoothSocket)m.invoke(dev, devUUID);
Log.d("TEST", "Method Invoked");
bs.connect();
Log.d("TEST", "Connected to socket");
bs.close();
Log.d("TEST", "Closed Socket");
}
While looking for the solution of similar problem in my app, I have found this blog from code.google.com
It will help all those who are still looking for this problem solution on SO
http://mobisocial.stanford.edu/news/2011/03/bluetooth-reflection-and-legacy-nfc/ (link not working anymore)
The solution has become very simple now. Just include InsecureBluetooth.java in your project and change 2 lines in BluetoothChatService.java.
tmp = InsecureBluetooth.listenUsingRfcommWithServiceRecord(mAdapter, NAME, MY_UUID, true);
and
tmp = InsecureBluetooth.createRfcommSocketToServiceRecord(device, MY_UUID, true);
Thats it !