Develop Reference

c# and Android tcp communication on public ip

I'm writing app on android, which would communicate with c# server via TCP protocol. My code works fine when I use wi-fi and now I want to change it that it would work even if android client would use mobile data
Server in c# (only recive and send data):
static void Main(string[] args)
{
//setup
Program prog = new Program();//to run non-static void from static context
//main server
try
{
IPAddress ipAd = IPAddress.Parse("192.168.x.xxx");
// Initializes the Listener
TcpListener myList = new TcpListener(ipAd, 11000);
/* Start Listeneting at the specified port */
myList.Start();
//label com
com:
//accept connection
Socket s = myList.AcceptSocket();
Console.WriteLine("Connection accepted from " + s.RemoteEndPoint);
//recive data
byte[] b = new byte[100];
int k = s.Receive(b);
char cc = ' ';
string text = null;//wil produce recived text
Console.Write("Recieved: ");
for (int i = 0; i < k - 1; i++)
{
Console.Write(Convert.ToChar(b[i]));
cc = Convert.ToChar(b[i]);
text += cc.ToString();
}
Console.WriteLine();
//analyze text
string reply = prog.analyzeText(text);
//send reply
ASCIIEncoding asen = new ASCIIEncoding();//is using to encode reply<string> to possible to send format
s.Send(asen.GetBytes(reply));//send
s.Close();
/* clean up */
goto com;
s.Close();
myList.Stop();
Console.ReadLine();
}
catch (Exception e)
{
Console.WriteLine("Error: " + e.StackTrace);
Console.ReadLine();
}
}
and android client code:
private String connectSocket(String msg) {//send and receive data from server
try {
InetAddress serverAddr = InetAddress.getByName("192.168.x.xxx");
Socket socket = new Socket(serverAddr, 11000);
//define PrintWriter
PrintWriter out = null;
try {
out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);
final BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
out.println(msg);
String text = "";
String finalText = "";
while ((text = in.readLine()) != null) {
finalText += text;
}
socket.close();
return finalText;
} catch (Exception e) {
Toast.makeText(getApplicationContext(),"Something went wrong.\nTry again in few minutes",Toast.LENGTH_SHORT).show();
return "exception";
} finally {
socket.close();
}
} catch (UnknownHostException e) {
return "UnknownHostException";
} catch (IOException e) {
return "IOException";
}
}
PS. sorry for my english, but I started learning it only 1 year ago

There's no code changes needed. You might need to set up your network correctly so there's no firewalls in the way around your test server (and that may include talking to your ISP, if they have a firewall preventing incoming connections). But standard socket communication works over wifi or mobile.

TCP Client stalled until disconnected by the server

When trying to receive a string or file content (as string) via TCP I am stuck with an issue wher the receiving works in general, but the line
print("TCP -> Data received:\n" + file + "\n\n" + totalrecbytes + " Bytes");
is kind of stalled until I activelly disconnect from the server side. Than it works as expected.
I debugged and receiving the data inside the
while ((recBytes = netstream.Read(bytes, 0, bytes.Length)) > 0)
loop works just fine. It also ends the loop in the correct moment. But after that simply nothing happens. I get no errors, am not "trapped" in any loop but also do not get the expected output of
print("TCP -> Data received:\n" + file + "\n\n" + totalrecbytes + " Bytes");
until I disconnect from the server side. Than I see the expected output and the client is disconnected.
Here is the implementation (original source)
private Thread _tcpThread;
private TcpClient _socketConnection;
public void Connect()
{
try
{
_tcpThread = new Thread(ReciveDataClient);
_tcpThread.IsBackground = true;
_tcpThread.Start();
}
catch (Exception e)
{
print(e.Message);
}
}
private void ReciveDataClient()
{
try
{
_socketConnection = new TcpClient("xxx.xxx.xxx.xxx", 54321);
print(this, "TCP -> Connection Success!");
}
catch (Exception e)
{
print("connection error: " + e.Message)
return;
}
try
{
var bytes = new byte[BUFFER_SIZE];
while (_socketConnection.Connected)
{
if (_socketConnection.Available <= 0) continue;
// Get a stream object for reading
var netstream = _socketConnection.GetStream();
int totalrecbytes = 0;
int recBytes;
string file = "";
// Read incomming stream into byte arrary.
while ((recBytes = netstream.Read(bytes, 0, bytes.Length)) > 0)
{
var incommingData = new byte[recBytes];
Array.Copy(bytes, 0, incommingData, 0, recBytes);
// Convert byte array to string message.
var serverMessage = Encoding.ASCII.GetString(incommingData);
file += serverMessage;
totalrecbytes += recBytes;
}
print("TCP -> Data received:\n" + file + "\n\n" + totalrecbytes + " Bytes");
netstream.Close();
}
print("TCP -> connection was terminated by the server");
}
catch (Exception e)
{
print(e.Message)
return;
}
}
I would expect that I can maintain the connection alive but still receive the data correctly and communicate with the server on a persistent TCP connection.
What am I missing or doing wrong here?
The only workarround I could find so far is allways disconnect from the server side after sending data and in my code wrap the whole ReceiveDataClient in a while loop like
private void ReciveDataClient()
{
while (true)
{
try
{
_socketConnection = new TcpClient(_server.ToString(), _server.Port);
//...
in order to immediately start a new connection after the server sent some data and disconnected the client.

Thanks to the help of Damien_The_Unbeliever and Immersive I could figure it out. It really helps to read the docs from time to time especially if it is the first time you use something ^^
NetworkStream.Read is a blocking call and as the doc states
returns: The number of bytes read from the NetworkStream, or 0 if the socket is closed.
so ofcourse the while loop actually never terminated.
So adopting the example provided there worked for me except that if the server ended the connection I got another issue so instead of checking for _socketConnection.IsConnected I used the marked answer from this post so all together this works for me now
private Thread _tcpThread;
private TcpClient _socketConnection;
public void Connect()
{
if(_socketConnection != null) return;
try
{
_tcpThread = new Thread(ReciveDataClient);
_tcpThread.IsBackground = true;
_tcpThread.Start();
}
catch (Exception e)
{
print("TCP -> Thread error: " + e.Message);
}
}
public void Disconnect()
{
if(_socketConnection = null) return;
_tcpThread.Abort();
}
private void ReciveDataClient()
{
try
{
_socketConnection = new TcpClient("xxx.xxx.xxx.xxx", 54321);
print(this, "TCP -> Connection Success!");
}
catch (Exception e)
{
print("TCP -> connection error: " + e.Message)
return;
}
try
{
while(true)
{
// Get a stream object for reading
var netstream = _socketConnection.GetStream();
//Check if still connected
if(_socketConnection.Client.Poll(0, SelectMode.SelectRead))
{
byte[] buff = new byte[1];
if( _socketConnection.Client.Receive( buff, SocketFlags.Peek ) == 0 )
{
// Server disconnected or connection lost
break;
}
}
// Check to see if this NetworkStream is readable.
if(myNetworkStream.CanRead)
{
byte[] myReadBuffer = new byte[BUFFER_SIZE];
StringBuilder myCompleteMessage = new StringBuilder();
int numberOfBytesRead = 0;
int totalBytesReceived = 0;
// Incoming message may be larger than the buffer size.
do
{
numberOfBytesRead = myNetworkStream.Read(myReadBuffer, 0, myReadBuffer.Length);
myCompleteMessage.AppendFormat("{0}", Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead));
totalBytesReceived += numberOfBytesRead;
}
while(myNetworkStream.DataAvailable);
// Print out the received message to the console.
print("TCP -> Data received:\n" + myCompleteMessage.ToString() + "\n\n" + totalrecbytes + " Bytes");
}
else
{
//Prevent a direct loop
Thread.Sleep(100);
}
}
print("TCP -> connection was terminated by the server");
}
catch(ThreadAbortException)
{
print("TCP -> Disconnected");
}
catch(Exception e)
{
print(e.Message)
}
// Clean up
_socketConnection?.Close();
_socketConnection?.Dispose();
_socketConnection = null;
}

Transfer String via TCP/IP to multiple computers

This code currently takes kinect Body data and writes it in an Excel Worksheet. I have another code that is able to create a TCP/IP connection between two computers. How would I best combine these two ideas?
I require this Joint String Data to be sent over the network and collected by another server computer, in real-time, not in an excel file. Do you have any suggestions ?
In other words, I have some Server code, but i want the server to listen for the Kinect String Data that the client code (Another computer) is generating and currently is writing it to a local excel file.
Client Side
...
_recordBody = !_recordBody;
if (_recordBody == false)
{
recordButton.Content = "Record";
return;
}
recordButton.Content = "Stop Recording";
currentTrackingID = 0;
// create a csv file and write file header
string currPath = System.IO.Directory.GetCurrentDirectory();
string folder = "recordings";
string recordPath = System.IO.Path.Combine(currPath, folder);
if (!Directory.Exists(recordPath))
{
Directory.CreateDirectory(recordPath);
}
timeRecordingStarted = DateTime.Now;
string filename = timeRecordingStarted.ToString("yyyy-MM-dd HH-mm-ss");
filename = filename + ".csv";
filePath = System.IO.Path.Combine(recordPath, filename);
string[] writtentext = {"time," + "headX," +
"headY," +
"headZ," +
"headS," +
"neckX," +
"neckY," +
"neckZ," +
"neckS," +
"spineShoulderX," +
"spineShoulderY," +
"spineShoulderZ," +
...
"handLeftY," +
"handLeftZ," +
"handLeftS," +
"handTipRightX," +
"handTipRightY," +
"handTipRightZ," +
"handTipRightS," +
"handTipLeftX," +
"handTipLeftY," +
"handTipLeftZ," +
"handTipLeftS"
};
File.WriteAllLines(filePath, writtentext);
...
Server Code
static TcpListener tcpListener = new TcpListener(10);
static void Listeners()
{
Socket socketForClient = tcpListener.AcceptSocket();
if (socketForClient.Connected)
{
Console.WriteLine("Client:"+socketForClient.RemoteEndPoint+" now connected to server.");
NetworkStream networkStream = new NetworkStream(socketForClient);
System.IO.StreamWriter streamWriter =
new System.IO.StreamWriter(networkStream);
System.IO.StreamReader streamReader =
new System.IO.StreamReader(networkStream);
{
string theString = streamReader.ReadLine();
Console.WriteLine("Message recieved by client:" + theString);
if (theString == "exit")
break;
}
streamReader.Close();
networkStream.Close();
streamWriter.Close();
//}
}
socketForClient.Close();
Console.WriteLine("Press any key to exit from server program");
Console.ReadKey();
}
public static void Main()
{
//TcpListener tcpListener = new TcpListener(10);
tcpListener.Start();
Console.WriteLine("************This is Server program************");
Console.WriteLine("How many clients are going to connect to this server?:");
int numberOfClientsYouNeedToConnect =int.Parse( Console.ReadLine());
for (int i = 0; i < numberOfClientsYouNeedToConnect; i++)
{
Thread newThread = new Thread(new ThreadStart(Listeners));
newThread.Start();
}
}
}

TcpListener AcceptSocket() accepts two connections for each single GET request

I have this web server program up and running, using TcpListener. The problem is that for each get request made through web browser (or chrome Postman extension), it captures two requests.
namespace Server
{
class WebServer2
{
private TcpListener listener;
private int port = 8080;
public WebServer2()
{
try
{
listener = new TcpListener(IPAddress.Parse("127.0.0.1"), port);
listener.Start();
Console.WriteLine("Listening...");
//start the thread which calls the method 'StartListen'
Thread th = new Thread(new ThreadStart(StartListen));
th.Start();
}
catch (Exception e)
{
Console.WriteLine("An Exception Occurred While Listening: " + e.ToString());
}
}
//Recieve Request
public void StartListen()
{
int iStartPos = 0;
String sRequest;
String sRequestedFile;
String sResponse = "";
while (true)
{
//Accept a new connection
Socket socket = listener.AcceptSocket();
if (socket.Connected)
{
Console.WriteLine("\nClient Connected");
Console.WriteLine("----------------");
//Receive data from the client
Byte[] bReceive = new Byte[1024];
int i = socket.Receive(bReceive, bReceive.Length, 0);
//Convert Byte to String
string sBuffer = Encoding.ASCII.GetString(bReceive);
//Only GET Request is accepted
if (sBuffer.Substring(0, 3) != "GET")
{
Console.WriteLine("Not a Get Request.");
socket.Close();
continue;
}
// Look for HTTP request
iStartPos = sBuffer.IndexOf("HTTP", 1);
// Get the HTTP text and version e.g. it will return "HTTP/1.1"
string sHttpVersion = sBuffer.Substring(iStartPos, 8);
// Extract the Requested Type and Requested file/directory
sRequest = sBuffer.Substring(0, iStartPos - 1);
//If file name not provided
if (sRequest.IndexOf(".") < 1)
{
Console.WriteLine("File name not Provided!");
socket.Close();
continue;
}
//Extract the requested file name
iStartPos = sRequest.LastIndexOf("/") + 1;
sRequestedFile = sRequest.Substring(iStartPos);
Console.WriteLine("Requested File: " + sRequestedFile);
int iTotBytes = 0;
sResponse = "";
FileStream fs = new FileStream(sRequestedFile, FileMode.Open, FileAccess.Read, FileShare.Read);
BinaryReader reader = new BinaryReader(fs);
byte[] bytes = new byte[fs.Length];
int read;
while ((read = reader.Read(bytes, 0, bytes.Length)) != 0)
{
// Read from the file and write the data to the network
sResponse = sResponse + Encoding.ASCII.GetString(bytes, 0, read);
iTotBytes = iTotBytes + read;
}
reader.Close();
fs.Close();
SendHeader(sHttpVersion, "text/html", iTotBytes, " 200 OK", ref socket);
SendToBrowser(bytes, ref socket);
socket.Send(bytes, bytes.Length, 0);
socket.Close();
}
}
}
// Overloaded Function, takes string, convert to bytes and calls
// overloaded sendToBrowserFunction.
public void SendToBrowser(String sData, ref Socket socket)
{
SendToBrowser(Encoding.ASCII.GetBytes(sData), ref socket);
}
/// Sends data to the browser (client)
public void SendToBrowser(Byte[] bSendData, ref Socket socket)
{
int numBytes = 0;
try
{
if (socket.Connected)
{
if ((numBytes = socket.Send(bSendData, bSendData.Length, 0)) == -1)
Console.WriteLine("Socket Error");
}
else
Console.WriteLine("Connection Dropped!");
}
catch (Exception e)
{
Console.WriteLine("Error: {0} ", e);
}
}
// This function send the Header Information to the client (Browser)
public void SendHeader(string sHttpVersion, string sMIMEHeader, int iTotBytes, string sStatusCode, ref Socket socket)
{
String sBuffer = "";
Byte[] bSendData;
if (sStatusCode.Equals("404") || sStatusCode.Equals("400"))
{
sBuffer = sBuffer + sHttpVersion + sStatusCode + "\r\n";
sBuffer = sBuffer + "Server: MyServer\r\n";
sBuffer = sBuffer + "Content-Length: " + 0 + "\r\n\r\n";
bSendData = Encoding.ASCII.GetBytes(sBuffer);
SendToBrowser(bSendData, ref socket);
}
else
{
sBuffer = sBuffer + sHttpVersion + sStatusCode + "\r\n";
sBuffer = sBuffer + "Server: MyServer\r\n";
sBuffer = sBuffer + "Content-Type: " + sMIMEHeader + "\r\n";
sBuffer = sBuffer + "Accept-Ranges: bytes\r\n";
sBuffer = sBuffer + "Content-Length: " + iTotBytes + "\r\n\r\n";
bSendData = Encoding.ASCII.GetBytes(sBuffer);
SendToBrowser(bSendData, ref socket);
}
}
}
}
Single request made by chrome against http://localhost:8080/page1.html
Request made by Postman Extension
The funny thing is, everything works find when I send request through my client program (using TcpClient).

I tested your server and got similar results:
Chrome automatically asks for a favicon.ico file for every request. This generates the extra GET request to your server.
Firefox doesn't do this and simply generates one request per refresh.
Then there is a second problem I experienced, which is the one in your Postman screenshot.
Chrome (including the Postman Extension running inside it) reconnects
without sending anything, so the server "hangs" until you get a
response filled with \0 (nul-characters).
This is part of Chrome's prediction service to load subsequent requests faster. You could disable this behavior under Settings (advanced) > Privacy:
In your server implementation, this results in the "Not a Get Request" output if no subsequent GET request follows (instead, Chrome sends \0 to signal its not sending anything anyway).
Note: I didn't experience any of this in the actual Postman application.
While the server waits for chrome to send a request, it cannot service any other requests. To prevent this from happening, consider using an asynchronous approach.

Android and c# tcp communication

I want to send a message from a C# application to the Android emulator or device over TCP. I have searched on Google and got the maximum results for Android client and C# server but not what I want to acheive.
Here is what I have tried; maybe I am going about it the wrong way but what I want is to send a message over TCP to an Android device.
Server Code to send a message:
private static int port = 4444;
private static TcpListener listener;
private static Thread thread;
private static int clientId = 0;
listener = new TcpListener(new IPAddress(new byte[] { 127, 0, 0, 1 }), port);
thread = new Thread(new ThreadStart(Listen));
thread.Start();
private static void Listen()
{
listener.Start();
MessageBox.Show("Listening on: " + port.ToString());
while (true)
{
MessageBox.Show("Waiting for connection....");
MessageBox.Show("Client No: " + clientId);
TcpClient client = listener.AcceptTcpClient();
Thread listenThread = new Thread(new ParameterizedThreadStart(ListenThread));
listenThread.Start(client);
}
}
private static void ListenThread(Object client)
{
NetworkStream netstream = ((TcpClient)client).GetStream();
MessageBox.Show("Request made");
clientId = clientId + 1;
// String message = "Hello world";
byte[] resMessage = Encoding.ASCII.GetBytes(clientId.ToString());
netstream.Write(resMessage, 0, resMessage.Length);
netstream.Close();
}
Client Code
private TextView textDisplay;
Socket socket;
private static final int TCP_SERVER_PORT = 4444;
ServerSocket ss = null;
try {
ss = new ServerSocket(TCP_SERVER_PORT);
//ss.setSoTimeout(10000);
//accept connections
Socket s = ss.accept();
BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
//receive a message
String incomingMsg = in.readLine() + System.getProperty("line.separator");
Log.d("TcpServer", "received: " + incomingMsg);
textDisplay.append("received: " + incomingMsg);
//send a message
String outgoingMsg = "goodbye from port " + TCP_SERVER_PORT + System.getProperty("line.separator");
out.write(outgoingMsg);
out.flush();
Log.d("TcpServer", "sent: " + outgoingMsg);
textDisplay.append("sent: " + outgoingMsg);
//SystemClock.sleep(5000);
s.close();
} catch (InterruptedIOException e) {
//if timeout occurs
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (ss != null) {
try {
ss.close();
} catch (IOException e) {
Log.d("Error",e.toString());
}
}
}

The problem lies in your Client code.
A socket is opened between two parties, one that plays the role of the listener / server that does bind->listen->accept and a client that connect
In your code there are two problems:
Your client should connect and not accept
Both your client and your server will try to read from the socket and write afterwards. There would be no problem if your read and write operations from the socket were on different threads.In your case this will result in a deadlock.
If you want both operations to be done on the same thread , sequentially then your client and server should perform the read and write in opposite order :
Client : read -> write
Server: write-> read