I've been trying to send data from an android device to a computer by hosting a virtual network on the computer and connecting the android device to it (basically sending data over WLAN).
However, upon debugging the android app it always throws the following exception:
System.Net.Sockets.SocketException (0x80004005): Network subsystem is down.
Android App Code Snippet:
namespace TestWifiApp
{
[Activity(Label = "TestWifiApp", MainLauncher = true)]
public class MainActivity : Activity
{
string bssid = "00:18:39:12:2b:e9";
const string ssid = "TEST";
const string password = "123456abc";
const string kioskIp = "192.168.137.11";
const int kioskPort = 2201;
void sendData(string ntlId)
{
try {
System.Net.Sockets.Socket soc = new System.Net.Sockets.Socket(AddressFamily.InterNetwork, System.Net.Sockets.SocketType.Stream, System.Net.Sockets.ProtocolType.Tcp);
System.Net.IPAddress ipAdd = System.Net.IPAddress.Parse(kioskIp);
System.Net.IPEndPoint ep = new System.Net.IPEndPoint(ipAdd, kioskPort);
soc.Connect(ep);
byte[] data = ASCIIEncoding.ASCII.GetBytes(ntlId);
soc.Send(data);
soc.Disconnect(false);
soc.Close();
Log.Debug("TEST", "Data sent");
}
catch(Exception ex)
{
Log.Debug("TEST",ex.ToString());
}
}
}
Server Code:
class Program
{
const int PORT_NO = 2201;
static Socket serverSocket;
static void Main(string[] args)
{
//---listen at the specified IP and port no.---
Console.WriteLine("Listening...");
serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
serverSocket.Bind(new IPEndPoint(IPAddress.Any, PORT_NO));
serverSocket.Listen(4); //the maximum pending client, define as you wish
serverSocket.BeginAccept(new AsyncCallback(acceptCallback), null);
string result = "";
do
{
result = Console.ReadLine();
} while (result.ToLower().Trim() != "exit");
}
private const int BUFFER_SIZE = 4096;
private static byte[] buffer = new byte[BUFFER_SIZE]; //buffer size is limited to BUFFER_SIZE per message
private static void acceptCallback(IAsyncResult result)
{ //if the buffer is old, then there might already be something there...
Socket socket = null;
try
{
socket = serverSocket.EndAccept(result); // The objectDisposedException will come here... thus, it is to be expected!
//Do something as you see it needs on client acceptance
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(receiveCallback), socket);
serverSocket.BeginAccept(new AsyncCallback(acceptCallback), null); //to receive another client
}
catch (Exception e)
{ // this exception will happen when "this" is be disposed...
//Do something here
Console.WriteLine(e.ToString());
}
}
const int MAX_RECEIVE_ATTEMPT = 10;
static int receiveAttempt = 0; //this is not fool proof, obviously, since actually you must have multiple of this for multiple clients, but for the sake of simplicity I put this
private static void receiveCallback(IAsyncResult result)
{
Socket socket = null;
try
{
socket = (Socket)result.AsyncState; //this is to get the sender
if (socket.Connected)
{ //simple checking
int received = socket.EndReceive(result);
if (received > 0)
{
byte[] data = new byte[received]; //the data is in the byte[] format, not string!
Buffer.BlockCopy(buffer, 0, data, 0, data.Length); //There are several way to do this according to https://stackoverflow.com/questions/5099604/any-faster-way-of-copying-arrays-in-c in general, System.Buffer.memcpyimpl is the fastest
//DO SOMETHING ON THE DATA int byte[]!! Yihaa!!
Console.WriteLine(Encoding.UTF8.GetString(data)); //Here I just print it, but you need to do something else
//Message retrieval part
//Suppose you only want to declare that you receive data from a client to that client
string msg = "I receive your message on: " + DateTime.Now;
socket.Send(Encoding.ASCII.GetBytes(msg)); //Note that you actually send data in byte[]
Console.WriteLine("I sent this message to the client: " + msg);
receiveAttempt = 0; //reset receive attempt
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(receiveCallback), socket); //repeat beginReceive
}
else if (receiveAttempt < MAX_RECEIVE_ATTEMPT)
{ //fail but not exceeding max attempt, repeats
++receiveAttempt; //increase receive attempt;
socket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(receiveCallback), socket); //repeat beginReceive
}
else
{ //completely fails!
Console.WriteLine("receiveCallback fails!"); //don't repeat beginReceive
receiveAttempt = 0; //reset this for the next connection
}
}
}
catch (Exception e)
{ // this exception will happen when "this" is be disposed...
Console.WriteLine("receiveCallback fails with exception! " + e.ToString());
}
}
}
I've tried connecting another computer to the hosted network and sending data to that computer, but the same exception is thrown.
