Develop Reference

Server Timeout C#

So, I'm developing a client-side application in C# that connects to a server side application (also written in C#). To begin with, I am just trying to get the applications to successfully communicate with one another. Currently, I have both the client and server running on the same device.
Server Side
On the server side, I'm using a TcpListener to accept a socket, printing out that it has connected for debugging purposes, receiving a request, and sending a response. The code can be found below:
Server Side Code:
while (true)
{
// Accept a new connection
Socket socket = socketListener.AcceptSocket();
if (socket.Connected)
{
Console.WriteLine("\nClient Connected!!\n==================\nClient IP {0}\n", socket.RemoteEndPoint);
// Make a byte array and receive data from the client
byte[] receive = new byte[1024];
_ = socket.Receive(receive, receive.Length, 0);
// Convert byte to string
string buffer = Encoding.ASCII.GetString(receive);
string response = "Test response";
int numBytes = 0;
try
{
if (socket.Connected)
{
if ((numBytes = socket.Send(data, data.Length, 0)) == -1)
Console.WriteLine("Socket Error: cannot send packet");
else
Console.WriteLine("No. of bytes sent {0}", numBytes);
}
else
{
Console.WriteLine("Connection Dropped...");
}
}
catch (Exception e)
{
Console.WriteLine("An exception has occurred: " + e.ToString());
}
}
}
Client Side
On the client side, I'm using a TcpClient to connect to the server using an IP address (In this case it's 127.0.0.1), establishing a NetworkStream object, sending a request, and reading a response.
Client-Side Code:
private static readonly TcpClient socket = new TcpClient();
private const string IP = "127.0.0.1";
private const int PORT = 46495;
static void Main(string[] args)
{
try
{
socket.Connect(IP, PORT);
}
catch (Exception)
{
Console.WriteLine("Error connecting to the server.");
return;
}
NetworkStream stream = socket.GetStream();
stream.ReadTimeout = 2000;
string request = "Test Request";
byte[] bytes = Encoding.UTF8.GetBytes(request);
stream.Write(bytes, 0, bytes.Length);
StreamReader reader = new StreamReader(stream, Encoding.UTF8);
try
{
string response = reader.ReadToEnd();
Console.WriteLine(response);
}
catch(Exception e)
{
Console.WriteLine(e);
}
}
The Output
On the server side, everything appears to be fine. The client connects successfully with the expected IP address, I get the expected request, and the correct response appears to have been sent successfully.
The client-side is where it gets more complicated. Where I would expect the "Test Response" response, instead I get a SocketException that from what I understand indicates a timeout??? The full output can be found below:
System.IO.IOException: Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or an established connection failed because the connected host has failed to respond...
---> System.Net.Sockets.SocketException (10060): A connection attempt failed because the connected party did not properly respond after a period of time, or an established connection failed because the connected host has failed to respond.
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
--- End of inner exception stack trace ---
at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.IO.StreamReader.ReadBuffer()
at System.IO.StreamReader.ReadToEnd()
at Client.Client.Main(String[] args) in C:\Dev\Project Orange Sunshine\Project Orange Sunshine\Client\Client.cs:line 38
What I have tried
To begin I wanted to ensure that my server was in fact sending a response in the first place. To test this, I tried accessing the server application through a web browser. Sure enough, I got a blank page with the expected "Test Response" text in the top left corner. This, to me, indicates my server application is working as expected.
Through some googling, I have found a variety of answers to similar questions stating that it is likely that the Windows Defender Firewall is blocking the port that is being used. For testing purposes, I tried disabling the firewall entirely for private networks such as the one that I am on. This didn't change anything, unfortunately.
I feel like I am missing something obvious and any input would be greatly appreciated.
Cheers!

StreamReader.ReadToEnd() on a NetworkStream will only return once the "end" of the stream is reached, which doesn't happen in your example; thus, the StreamReader times out.
You should fix this by using the lower-level NetworkStream.Read method to read from the stream:
var buffer = new byte[4096];
var bytesRead = stream.Read(buffer, 0, buffer.Length);
Console.WriteLine("Read {0} bytes", bytesRead);
string response = Encoding.UTF8.GetString(buffer, 0, bytesRead);
Console.WriteLine(response);
To make this test program more robust, you will also need to introduce "framing", i.e., some way for the server to indicate to the client that it can stop reading. This can be a terminator suffix, such as \r\n used by HTTP, or a length prefix that is sent upfront to tell the client how many more bytes to read.

How to communicate between two Unity apps with TCP?

Update
I figured out what the problem was. I was trying to move too much data over TCP, and it was causing freeze-ups. For some reason, this wasn't manifesting in the editor...who knows for what reason. If anyone else stumbles upon this problem (in a program like Unity, where functions are looping constantly and data is always being processed), consider that you're moving too much irrelevant data.
Original Post
I've run into quite the problem, and I'm hoping I can receive some guidance.
In short, I'm wondering how to use TCP to communicate two Unity apps over the same computer. I've gotten it functioning in editor, but when both apps are built, communication quickly breaks down.
This is really stumping me, because I don't understand why an app would work in the Editor environment, but not in the official build.
When I use TCP to communicate between two Unity apps (on the same computer), it works so long as one of them is kept in the Unity environment. That is, if I build one app, and open the other in the Unity editor, TCP communication works flawlessly.
Here is some more background: One of my apps is functioning as a User Interface, and the other is interfacing with a Looking Glass to provide a holographic display of in-game objects. Originally, they were combined into one App - but I had a lot of trouble getting Unity's multidisplay support to function between two monitors of different resolutions. Looking Glass factory even provides a prefab to do just this, but it is broken in the current SDK. So I have resorted to using sockets to interface between two apps, one for each monitor.
I'm using C#'s TCP listener class: https://learn.microsoft.com/en-us/dotnet/api/system.net.sockets.tcplistener?view=netframework-4.8
And TCP client class: https://learn.microsoft.com/en-us/dotnet/api/system.net.sockets.tcpclient?view=netframework-4.8
Presently, the UI is acting as the TCPListener, and the application that produces holograms is the TCPClient. Within each of these applications, I'm using two Queues - an IncomingMessages queue and an Outgoing Messages queue - which are global variables shared between the main thread and the networking thread.
TCP Listener:
private void Start()
{
incomingMessages = new Queue();
outgoingMessages = new Queue();
Application.runInBackground = true;
thread = new Thread(new ThreadStart(Receive));
thread.Start();
//stuff happens that's irrelevant to this question. And then...
}
void Receive()
{
TcpListener server = null;
try
{
// Set the TcpListener on port 13000.
Int32 port = 13000;
IPAddress localAddr = IPAddress.Parse("127.0.0.1");
// TcpListener server = new TcpListener(port);
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// Buffer for reading data
Byte[] bytes = new Byte[256];
String data = null;
// Enter the listening loop.
Debug.Log("About to reenter main while in Server...");
while (threadContinue)
{
Debug.Log("Waiting for a connection... ");
// Perform a blocking call to accept requests.
// You could also user server.AcceptSocket() here.
TcpClient client = server.AcceptTcpClient();
Debug.Log("Connected!");
data = null;
// Get a stream object for reading and writing
NetworkStream stream = client.GetStream();
int i;
// Loop to receive all the data sent by the client.
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
// Translate data bytes to a ASCII string.
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
Debug.Log("Received from Client: " + data);
lock (this)
incomingMessages.Enqueue(data);
string response = supplyData();
byte[] msg = System.Text.Encoding.ASCII.GetBytes(response);
// Send back a response.
stream.Write(msg, 0, msg.Length);
Debug.Log("Sent to Client: " + response);
}
// Shutdown and end connection
client.Close();
}
}
catch (SocketException e)
{
Debug.Log("SocketException: ");
Debug.Log(e);
}
finally
{
// Stop listening for new clients.
server.Stop();
}
Debug.Log("Exiting 'Receive'");
}
And here is the TCP Client. It attempts to connect a regular intervals, and also whenever new data is available. This is so that it can receive information from the server regularly and share new data whenever it is available:
void Start()
{
//prepare networking
Application.runInBackground = true;
outgoingMessages = new Queue();
incomingMessages = new Queue();
thread = new Thread(new ThreadStart(Connect));
thread.Start();
//stuff happens that's irrelevant to this question...
}
private void Connect()
{
String server = "127.0.0.1";
Int32 port = 13000;
string message = "";
while (threadContinue == true)
{
if (timeToConnect())
{
lastConnection = ourTime;
if (outgoingMessages.Count > 0)
message = outgoingMessages.Dequeue().ToString();
else
message = "Nothing to report.";
try
{
// Create a TcpClient.
// Note, for this client to work you need to have a TcpServer
// connected to the same address as specified by the server, port
// combination.
client = new TcpClient(server, port);
// Translate the passed message into ASCII and store it as a Byte array.
Byte[] data = System.Text.Encoding.ASCII.GetBytes(message);
// Get a client stream for reading and writing.
// Stream stream = client.GetStream();
stream = client.GetStream();
// Send the message to the connected TcpServer.
stream.Write(data, 0, data.Length);
Debug.Log("Sent to Server: " + message);
// Buffer to store the response bytes.
data = new Byte[256];
// String to store the response ASCII representation.
String responseData = String.Empty;
// Read the first batch of the TcpServer response bytes.
Int32 bytes = stream.Read(data, 0, data.Length);
responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes);
lock (this)
incomingMessages.Enqueue(responseData);
Debug.Log("Received from Server: " + responseData);
stream.Close();
client.Close();
}
catch (ArgumentNullException e)
{
Debug.Log("ArgumentNullException: ");
Debug.Log(e);
outgoingMessages.Enqueue(message);
}
catch (SocketException e)
{
Debug.Log("SocketException: ");
Debug.Log(e);
outgoingMessages.Enqueue(message);
}
}
}
}
private bool timeToConnect()
{
if ((ourTime - lastConnection > NETWORK_DELAY) || (outgoingMessages.Count > 0))
return true;
return false;
}
Instantiated in separate threads so that Unity's main thread can continue unhindered.
Again - it works in Editor, but when I build it, it breaks.

Update
I figured out what the problem was. I was trying to move too much data over TCP, and it was causing freeze-ups. For some reason, this wasn't manifesting in the editor...just in the exported app. Who knows for what reason. If anyone else stumbles upon this problem...where you're bypassing Unity's multidisplay functionality by building multiple apps that communicate over network...consider that you're burdening your queues with too much data.

TcpClient established, but TcpClient.getStream() fails

My Client class for synchronous message exchange:
public class AsClient
{
private TcpClient connection;
public AsClient(int serverPort, String ip)
{
connection = new TcpClient(ip, port);
}
public AsMessage sendMessage(AsMessage message)
{
System.Diagnostics.Debug.WriteLine("Connected: " + connection.Connected);
NetworkStream ns = connection.GetStream();
StreamReader reader = new StreamReader(ns);
StreamWriter writer = new StreamWriter(ns);
// Send Message:
String msgToSendEncoded = message.encode();
writer.WriteLine(msgToSendEncoded);
writer.WriteLine("\n"); // each message is terminated by a paragraph
writer.Flush();
// Receive Message:
String msgReceivedRaw = reader.ReadLine();
AsMessage response = AsMessage.decode(msgReceivedRaw);
reader.Dispose();
writer.Dispose();
ns.Close();
return response;
}
}
If I debug this application, the first message sent and response received works perfectly well, but as soon as I want to send the second message, TcpClient.getStream() fails with the InvalidOperationException, which states that the connection is not established anymore.
The problem is that I am not actively closing the connection anywhere. If I put connection.Connect(host,port) before calling getStream(), it fails with the exception that the socket is still connected, even though connection.Connected is false.
Any ideas to solve this issue?

As I have experience Dispose close the underlying stream.
So you close the connection on the Dispose.

I'm running into the same problem with this piece of code that replicates follows the steps in the MS documentation for GetStream(): https://learn.microsoft.com/en-us/dotnet/api/system.net.sockets.tcpclient.getstream?view=netframework-4.8
public void Send(String message)
{
try
{
// Translate the passed message into ASCII and store it as a Byte array.
Byte[] data = Encoding.ASCII.GetBytes(message);
// Get a client stream for reading and writing.
NetworkStream stream = Client.GetStream();
stream.Write(data, 0, data.Length);
stream.Close(); // this also closses the connection the server!
}
catch (Exception e)
{
LogException(e);
}
}
What we see on the server side is that:
1) The connection is established.
2) The message never arrives.
3) when the stream.Close() statement executes, the server reports that the client closed the connection.
Inspecting the properties of stream I can see that streams OWNS the socket. So, wen it closes it must also close its socket. How come???

Implementing an FTP Client in C# using TCP

I've been messing around with TCP sockets in C#, and I'm having some trouble communicating with an FTP server I have set up. I can connect initially and get the 220 message, but when I send the "USER nrcrast" command, I never get a response, and the DataAvailable property returns false. Anybody know what I'm doing wrong? Here's my code so far:
namespace TCPClient
{
public partial class TCPClientForm : Form
{
private TcpClient myClient;
NetworkStream stream;
public TCPClientForm()
{
InitializeComponent();
send();
}
void send()
{
while (true)
{
try
{
myClient = new TcpClient("nrcrast.dyndns.info", 21);
break;
}
catch (SocketException ex)
{
Console.WriteLine(ex.ToString());
}
}
stream = myClient.GetStream();
int sendOffset = 0;
int recOffset=0;
int dataLength;
Byte[] receiveData = new Byte[256];
// wait for a response
dataLength = stream.Read(receiveData, recOffset, receiveData.Length);
String recvdMessage = System.Text.Encoding.ASCII.GetString(receiveData, 0, dataLength);
Console.WriteLine(recvdMessage.ToString());
recOffset+=dataLength;
String message = "USER nrcrast";
Byte[] data = System.Text.Encoding.ASCII.GetBytes(message);
stream.Write(data, 0, data.Length);
sendOffset += data.Length;
// wait for a response
while (!stream.DataAvailable)
{
}
dataLength = stream.Read(receiveData, 0, receiveData.Length);
recvdMessage = System.Text.Encoding.ASCII.GetString(receiveData, 0, dataLength);
Console.WriteLine(recvdMessage.ToString());
}
}

A shoot in the dark, you need to put a carriage return and new line at the end of the command
String message = "USER nrcrast\r\n";

If you're interested in looking over someone's shoulder on a similar project (not saying its perfect), I did the same thing a long time ago (this was back in .net 1.1, and ported it to .net 2.0 when the ssl stream stuff was added).
there are some tricky pieces to the FTP protocols with respect to timings of when you send commands, when the server expects you to open the data connection, when you read the server response, and so forth (depending on active / passive modes).
anyway, feel free to look over My FTP Client Library source code for reference as you do your own implementation. it's a pretty complete implementation and does auth ssl/tls as well.

Reading Split TCP Packets

I have written most of the code to handle incoming packets for my server. The format for packets is always int/int/int/string/string, and the first int is the size of the packet. I need to figure out some way to check and see if the entire packet arrived or if I need to wait for more pieces to come in, however with the way I have written my code, I can't think of a good way. Any help would be great as my brain is probably overthinking this.
private void ReadClientPacket(object client)
{
TcpClient tcpClient = (TcpClient)client;
NetworkStream clientStream = tcpClient.GetStream();
while (true)
{
try
{
int packetsize;
// Create a new Packet Object and fill out the data from the incoming TCP Packets
RCONPacket packet = new RCONPacket();
using (BinaryReader reader = new BinaryReader(clientStream))
{
// First Int32 is Packet Size
packetsize = reader.ReadInt32();
packet.RequestId = reader.ReadInt32();
packet.ServerDataSent = (RCONPacket.SERVERDATA_sent)reader.ReadInt32();
Console.WriteLine("Packet Size: {0} RequestID: {1} ServerData: {2}", packetsize, packet.RequestId, packet.ServerDataSent);
// Read first and second String in the Packet (UTF8 Null Terminated)
packet.String1 = ReadBytesString(reader);
packet.String2 = ReadBytesString(reader);
Console.WriteLine("String1: {0} String2: {1}", packet.String1, packet.String2);
}
switch (packet.ServerDataSent)
{
case RCONPacket.SERVERDATA_sent.SERVERDATA_AUTH:
{
ReplyAuthRequest(packet.RequestId, clientStream);
break;
}
case RCONPacket.SERVERDATA_sent.SERVERDATA_EXECCOMMAND:
{
ReplyExecCommand();
break;
}
default:
{
break;
}
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
break;
}
}
tcpClient.Close();
}

What you have should work, as the underlying stream will wait for more data. That is, if you were to call clientStream.ReadByte and there aren't any bytes available, the method will block until data comes in or until the stream is closed--in this case, probably disconnected by the server.
BinaryReader will until there's enough data to satisfy the read request, so the code should work as expected.