Develop Reference

Socket Programming in C# Is this considered polling?

so I have been trying out socket programming in C# using code found online. When looking at this code from https://www.geeksforgeeks.org/socket-programming-in-c-sharp/
public static void ExecuteServer()
{
// Establish the local endpoint
// for the socket. Dns.GetHostName
// returns the name of the host
// running the application.
IPHostEntry ipHost = Dns.GetHostEntry(Dns.GetHostName());
IPAddress ipAddr = ipHost.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddr, 11111);
// Creation TCP/IP Socket using
// Socket Class Costructor
Socket listener = new Socket(ipAddr.AddressFamily,
SocketType.Stream, ProtocolType.Tcp);
try {
// Using Bind() method we associate a
// network address to the Server Socket
// All client that will connect to this
// Server Socket must know this network
// Address
listener.Bind(localEndPoint);
// Using Listen() method we create
// the Client list that will want
// to connect to Server
listener.Listen(10);
while (true) {
Console.WriteLine("Waiting connection ... ");
// Suspend while waiting for
// incoming connection Using
// Accept() method the server
// will accept connection of client
Socket clientSocket = listener.Accept();
// Data buffer
byte[] bytes = new Byte[1024];
string data = null;
while (true) {
int numByte = clientSocket.Receive(bytes);
data += Encoding.ASCII.GetString(bytes,
0, numByte);
if (data.IndexOf("<EOF>") > -1)
break;
}
Console.WriteLine("Text received -> {0} ", data);
byte[] message = Encoding.ASCII.GetBytes("Test Server");
// Send a message to Client
// using Send() method
clientSocket.Send(message);
// Close client Socket using the
// Close() method. After closing,
// we can use the closed Socket
// for a new Client Connection
clientSocket.Shutdown(SocketShutdown.Both);
clientSocket.Close();
}
}
catch (Exception e) {
Console.WriteLine(e.ToString());
}
}
}
}
I was wondering if the portion
while (true) {
int numByte = clientSocket.Receive(bytes);
data += Encoding.ASCII.GetString(bytes, 0, numByte);
if (data.IndexOf("<EOF>") > -1)
break;
}
is considered a polling method and also reason why we do not simply use
int numByte = clientSocket.Receive(bytes);
data = Encoding.ASCII.GetString(bytes, 0, numByte);
I have tried the above and it seems to work just as fine. So is there a reason why we use a infinite while loop that depends on the text to stop reading? I have found many sources which seems to use this method. Why is this so?

No response from socket

I have built a server and client which communicate via sockets.
When i run both the server and the client on the same machine both the server and the client receive the messages which are expected.
when i run the server on a VM or a different physical machine and the client on my main machine the server receives messages fine, but the client never receives the reply's
I have made sure to dissable windows firewall and my anti virus on all 3 machines (the 2 physical and one virtual one) to ensure its not a security issue.
The relevant code is as follows
SERVER
public class SynchronousSocketListener
{
// Incoming data from the client.
public static string data = null;
public void StartListening()
{
InstructionProcessor instructionProcessor = new InstructionProcessor();
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
// Dns.GetHostName returns the name of the
// host running the application.
IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket listener = new Socket(ipAddress.AddressFamily,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and
// listen for incoming connections.
try
{
listener.Bind(localEndPoint);
listener.Listen(10);
// Start listening for connections.
while (true)
{
Console.WriteLine("Waiting for a connection...");
// Program is suspended while waiting for an incoming connection.
Socket handler = listener.Accept();
data = null;
// An incoming connection needs to be processed.
while (true)
{
int bytesRec = handler.Receive(bytes);
data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
if (data.IndexOf("<EOF>") > -1)
{
break;
}
}
data = data.Substring(0, data.Length - 5);
// Show the data on the console.
string response = instructionProcessor.doSomething(data);
// Echo the data back to the client.
byte[] msg = Encoding.ASCII.GetBytes(response);
handler.Send(msg);
handler.Shutdown(SocketShutdown.Both);
handler.Close();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
}
}
CLIENT
public static string StartClient(string message, string ip)
{
// Data buffer for incoming data.
byte[] bytes = new byte[1024];
//Declare this at class scope level so it can be returned outside of try/catch blocks
string response = null;
// Connect to a remote device.
try
{
// Establish the remote endpoint for the socket.
// This example uses port 11000 on the local computer.
IPHostEntry ipHostInfo = Dns.GetHostEntry(ip);
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint remoteEP = new IPEndPoint(ipAddress, 11000);
//string hostName = Dns.GetHostName();
//string myIP = Dns.GetHostByName(hostName).AddressList[0].ToString(); ;
//Debug.WriteLine( ipAddress );
// Create a TCP/IP socket.
Socket sender = new Socket(ipAddress.AddressFamily,
SocketType.Stream, ProtocolType.Tcp);
// Connect the socket to the remote endpoint. Catch any errors.
try
{
sender.Connect(remoteEP);
Console.WriteLine("Socket connected to {0}",
sender.RemoteEndPoint.ToString());
// Encode the data string into a byte array.
byte[] msg = Encoding.ASCII.GetBytes(message + "<EOF>");
// Send the data through the socket.
int bytesSent = sender.Send(msg);
// Receive the response from the remote device.
int bytesRec = sender.Receive(bytes);
Console.WriteLine("Echoed test = {0}",
Encoding.ASCII.GetString(bytes, 0, bytesRec));
response = Encoding.ASCII.GetString(bytes, 0, bytesRec);
// Release the socket.
sender.Shutdown(SocketShutdown.Both);
sender.Close();
}
catch (ArgumentNullException ane)
{
Console.WriteLine("ArgumentNullException : {0}", ane.ToString());
}
catch (SocketException se)
{
Console.WriteLine("SocketException : {0}", se.ToString());
}
catch (Exception e)
{
Console.WriteLine("Unexpected exception : {0}", e.ToString());
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
return response;
}
}

Maybe because client is receiving more than 1024 byte. Try to increase the size of the received buffer.
Also add if (data.IndexOf("") > -1) into the client project.

C# How to do to send more message to Server with Client?

Im writing a Client Server Socket C# with TCP protocoll to create sort of "Client Ask, Server Answer" But when I Execute first command my client close. I should put while somewhere but I don't know where. here is the code:
CLIENT
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
public class SynchronousSocketClient
{
public static void StartClient()
{
// Data buffer for incoming data.
byte[] bytes = new byte[1024];
// Connect to a remote device.
try
{
// Establish the remote endpoint for the socket.
// This example uses port 11000 on the local computer.
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint remoteEP = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket sender = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Connect the socket to the remote endpoint. Catch any errors.
try
{
sender.Connect(remoteEP);
Console.WriteLine("Socket connected to {0}", sender.RemoteEndPoint.ToString());
Console.WriteLine("Insert text to send to server");
String a = Console.ReadLine(); //This is a test<EOF>
// Encode the data string into a byte array.
byte[] msg = Encoding.ASCII.GetBytes(a);
// Send the data through the socket.
int bytesSent = sender.Send(msg);
// Receive the response from the remote device.
int bytesRec = sender.Receive(bytes);
Console.WriteLine("Echoed test = {0}", Encoding.ASCII.GetString(bytes, 0, bytesRec));
// Release the socket.
//sender.Shutdown(SocketShutdown.Both);
//sender.Close();
}
catch (ArgumentNullException ane)
{
Console.WriteLine("ArgumentNullException : {0}", ane.ToString());
}
catch (SocketException se)
{
Console.WriteLine("SocketException : {0}", se.ToString());
}
catch (Exception e)
{
Console.WriteLine("Unexpected exception : {0}", e.ToString());
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
public static int Main(String[] args)
{
StartClient();
//To avoid Prompt disappear
Console.Read();
return 0;
}
}
SERVER
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Collections;
using System.IO;
//using System.Diagnostics;
public class SynchronousSocketListener
{
// Incoming data from the client.
public static string data = null;
public static void StartListening()
{
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
// Dns.GetHostName returns the name of the
// host running the application.
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and
// listen for incoming connections.
try
{
listener.Bind(localEndPoint);
listener.Listen(10);
byte[] msg = null;
// Start listening for connections.
while (true)
{
Console.WriteLine("Waiting for a connection...");
// Program is suspended while waiting for an incoming connection.
Socket handler = listener.Accept();
data = null;
// An incoming connection needs to be processed.
while (true)
{
bytes = new byte[1024];
int bytesRec = handler.Receive(bytes);
data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
if (data.Equals("ping"))
{
// Show the data on the console.
Console.WriteLine("Text received : {0}", data);
// Echo the data back to the client.
msg = Encoding.ASCII.GetBytes("pong");
handler.Send(msg);
break;
}
if (data.Equals("dir"))
{
// Show the data on the console.
Console.WriteLine("Text received : {0}", data);
// Echo the data back to the client.
msg = Encoding.ASCII.GetBytes(System.AppDomain.CurrentDomain.BaseDirectory);
handler.Send(msg);
break;
}
if (data.Equals("files"))
{
// Show the data on the console.
Console.WriteLine("Text received : {0}", data);
String files = "";
string[] fileEntries = Directory.GetFiles(System.AppDomain.CurrentDomain.BaseDirectory);
foreach (string fileName in fileEntries)
files += ProcessFile(fileName);
// Echo the data back to the client.
msg = Encoding.ASCII.GetBytes(files);
handler.Send(msg);
break;
}
}
// Show the data on the console.
//Console.WriteLine("Text received : {0}", data);
// Echo the data back to the client.
//byte[] msg = Encoding.ASCII.GetBytes(data);
//handler.Send(msg);
//handler.Shutdown(SocketShutdown.Both);
//handler.Close();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
}
public static String ProcessFile(string path)
{
return path += "\n\n" + path;
}
public static void ProcessDirectory(string targetDirectory)
{
// Process the list of files found in the directory.
string[] fileEntries = Directory.GetFiles(targetDirectory);
foreach (string fileName in fileEntries)
ProcessFile(fileName);
// Recurse into subdirectories of this directory.
string[] subdirectoryEntries = Directory.GetDirectories(targetDirectory);
foreach (string subdirectory in subdirectoryEntries)
ProcessDirectory(subdirectory);
}
public static int Main(String[] args)
{
StartListening();
return 0;
}
}
Now If you copy paste this code and execute Server and then Client, you can write something into CLient prompt and get an answers but at 2 attempt CLient close because there is no while that continues the process! I tried put while out of try and into but code crashed! An Help would be appreciate an help or solution is the same, just get an answer :)
Thank you everyone

I have limited knowledge working with sockets. However I know you should only call the following once:
Socket handler = listener.Accept();
I added a while loop under the above line and also removed your break statements at the end of your if conditions.
So the new code becomes:
CLIENT
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
public class SynchronousSocketClient
{
public static void StartClient()
{
// Data buffer for incoming data.
byte[] bytes = new byte[1024];
// Connect to a remote device.
try
{
// Establish the remote endpoint for the socket.
// This example uses port 11000 on the local computer.
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint remoteEP = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket sender = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Connect the socket to the remote endpoint. Catch any errors.
try
{
sender.Connect(remoteEP);
Console.WriteLine("Socket connected to {0}", sender.RemoteEndPoint.ToString());
while (true)
{
Console.WriteLine("Insert text to send to server");
String a = Console.ReadLine(); //This is a test<EOF>
// Encode the data string into a byte array.
byte[] msg = Encoding.ASCII.GetBytes(a);
// Send the data through the socket.
int bytesSent = sender.Send(msg);
// Receive the response from the remote device.
int bytesRec = sender.Receive(bytes);
Console.WriteLine("Echoed test = {0}", Encoding.ASCII.GetString(bytes, 0, bytesRec));
}
// Release the socket.
//sender.Shutdown(SocketShutdown.Both);
//sender.Close();
}
catch (ArgumentNullException ane)
{
Console.WriteLine("ArgumentNullException : {0}", ane.ToString());
}
catch (SocketException se)
{
Console.WriteLine("SocketException : {0}", se.ToString());
}
catch (Exception e)
{
Console.WriteLine("Unexpected exception : {0}", e.ToString());
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
public static int Main(String[] args)
{
StartClient();
//To avoid Prompt disappear
Console.Read();
return 0;
}
}
SERVER
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Collections;
using System.IO;
//using System.Diagnostics;
public class SynchronousSocketListener
{
// Incoming data from the client.
public static string data = null;
public static void StartListening()
{
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
// Dns.GetHostName returns the name of the
// host running the application.
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and
// listen for incoming connections.
while (true)
{
try
{
//if (!listener.IsBound)
//{
listener.Bind(localEndPoint);
//}
listener.Listen(10);
byte[] msg = null;
// Start listening for connections.
while (true)
{
Console.WriteLine("Waiting for a connection...");
// Program is suspended while waiting for an incoming connection.
Socket handler = listener.Accept();
while (true)
{
data = null;
// An incoming connection needs to be processed.
bytes = new byte[1024];
int bytesRec = handler.Receive(bytes);
data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
if (data.Equals("ping"))
{
// Show the data on the console.
Console.WriteLine("Text received : {0}", data);
// Echo the data back to the client.
msg = Encoding.ASCII.GetBytes("pong");
handler.Send(msg);
//break;
}
if (data.Equals("dir"))
{
// Show the data on the console.
Console.WriteLine("Text received : {0}", data);
// Echo the data back to the client.
msg = Encoding.ASCII.GetBytes(System.AppDomain.CurrentDomain.BaseDirectory);
handler.Send(msg);
//break;
}
if (data.Equals("files"))
{
// Show the data on the console.
Console.WriteLine("Text received : {0}", data);
String files = "";
string[] fileEntries = Directory.GetFiles(System.AppDomain.CurrentDomain.BaseDirectory);
foreach (string fileName in fileEntries)
files += ProcessFile(fileName);
// Echo the data back to the client.
msg = Encoding.ASCII.GetBytes(files);
handler.Send(msg);
//break;
}
}
// Show the data on the console.
//Console.WriteLine("Text received : {0}", data);
// Echo the data back to the client.
//byte[] msg = Encoding.ASCII.GetBytes(data);
//handler.Send(msg);
//handler.Shutdown(SocketShutdown.Both);
//handler.Close();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
}
public static String ProcessFile(string path)
{
return path += "\n\n" + path;
}
public static void ProcessDirectory(string targetDirectory)
{
// Process the list of files found in the directory.
string[] fileEntries = Directory.GetFiles(targetDirectory);
foreach (string fileName in fileEntries)
ProcessFile(fileName);
// Recurse into subdirectories of this directory.
string[] subdirectoryEntries = Directory.GetDirectories(targetDirectory);
foreach (string subdirectory in subdirectoryEntries)
ProcessDirectory(subdirectory);
}
public static int Main(String[] args)
{
StartListening();
return 0;
}
}

Send data between C# server and iOs

What I'm trying to do is to send data (under json format) from objective C (GCDAsyncSocket) to server C# by using socket.
Basically, the code below is for C# server and client objective C.
Server C# : ( I follow code from msdn)
public class SynchronousSocketClient {
public static void StartClient() {
// Data buffer for incoming data.
byte[] bytes = new byte[1024];
// Connect to a remote device.
try {
// Establish the remote endpoint for the socket.
// This example uses port 11000 on the local computer.
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName())
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint remoteEP = new IPEndPoint(ipAddress,11000);
// Create a TCP/IP socket.
Socket sender = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp );
// Connect the socket to the remote endpoint. Catch any errors.
try {
sender.Connect(remoteEP);
Console.WriteLine("Socket connected to {0}",
sender.RemoteEndPoint.ToString());
// Encode the data string into a byte array.
byte[] msg = Encoding.ASCII.GetBytes("This is a test<EOF>");
// Send the data through the socket.
int bytesSent = sender.Send(msg);
// Receive the response from the remote device.
int bytesRec = sender.Receive(bytes);
Console.WriteLine("Echoed test = {0}",
Encoding.ASCII.GetString(bytes,0,bytesRec));
// Release the socket.
sender.Shutdown(SocketShutdown.Both);
sender.Close();
} catch (ArgumentNullException ane) {
Console.WriteLine("ArgumentNullException : {0}",ane.ToString());
} catch (SocketException se) {
Console.WriteLine("SocketException : {0}",se.ToString());
} catch (Exception e) {
Console.WriteLine("Unexpected exception : {0}", e.ToString());
}
} catch (Exception e) {
Console.WriteLine( e.ToString());
}
}
public static int Main(String[] args) {
StartClient();
return 0;
}
}
Client: objective C
- (void)connect:(NSString *)host portNo:(NSString *)portno {
m_host = host ;
m_portno = [portno intValue];
if (m_soc == nil) {
m_soc = [[GCDAsyncSocket alloc] initWithDelegate:self delegateQueue:dispatch_get_main_queue()];
} else {
if (m_soc.isConnected) {
[m_soc disconnect];
}
}
NSError *error = nil;
m_isConnected = false ;
if (![m_soc connectToHost:m_host onPort:m_portno withTimeout:3.0 error:&error]) {
[self onError:#"Error in Connecting to Host."];
}
}
Unluckily, the result I got is
"err NSError * domain: #"GCDAsyncSocketErrorDomain" - code: 3"
This is just a connect only, have not done anything with send data yet.
Hope to get response from u all. Thanks much.

Why does Socket.Receive throw SocketException (10054) when remote host disconnects?

I used to write socket programs in C and can't understand why the above is happening.
My server blocks at a Receive call, when it returns 0, I break out of the while loop and shutdown the thread.
public class MyServer {
public MyServer() {
}
public void Init() {
ThreadPool.QueueUserWorkItem(StartListening);
while (true) {
Console.Read();
}
}
public void StartListening(Object state) {
// Establish the local endpoint for the socket.
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
try {
// Bind the socket to the local endpoint and listen for incoming connections.
listener.Bind(localEndPoint);
listener.Listen(100);
while (true) {
Console.WriteLine("Waiting for a connection...");
// get connection
Socket client = listener.Accept();
// push client to another thread
ThreadPool.QueueUserWorkItem(HandleClient, client);
}
} catch (Exception e) {
Console.WriteLine(e.ToString());
}
}
private void HandleClient(Object obj) {
// Get the socket that handles the client request.
Socket client = (Socket)obj;
// Create the state object.
StateObject state = new StateObject();
state.workSocket = client;
try {
while (true) {
int bytesRead = client.Receive(state.buffer);
Console.WriteLine("bytesRead=" + bytesRead);
// remote dc.
if (bytesRead == 0)
break;
String content = Encoding.ASCII.GetString(state.buffer, 0, bytesRead);
Console.WriteLine("Read {0} bytes from socket. \n Data : {1}", content.Length, content);
client.Send(state.buffer, 0, state.buffer.Length, 0);
}
} catch (SocketException e) {
Console.WriteLine("SocketException : {0}", e.ToString());
}
client.Shutdown(SocketShutdown.Both);
client.Close();
}
private void Send(Socket handler, String data) {
byte[] byteData = Encoding.ASCII.GetBytes(data);
// Begin sending the data to the remote device.
//handler.BeginSend(byteData, 0, byteData.Length, 0, new AsyncCallback(SendCallback), handler);
}
}
However, when I click on the close button ("x") of the client, server's Receive call throws a SocketException. According to MSDN's Remarks section, this shouldn't happen because I've satisfied both the connection-oriented part (see above) and client shutdown part(see below) conditions.
Client.cs (pseudo):
public class MyClient {
public void Init() {
byte[] bytes = new byte[1024];
Socket sender = null;
try {
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
IPEndPoint remoteEP = new IPEndPoint(ipAddress, 11000);
sender = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
sender.Connect(remoteEP);
Console.WriteLine("Socket connected to {0}",
sender.RemoteEndPoint.ToString());
while (true) {
// Encode the data string into a byte array.
String input = Console.ReadLine();
byte[] msg = Encoding.ASCII.GetBytes(input);
// Send the data through the socket.
int bytesSent = sender.Send(msg);
// Receive the response from the remote device.
int bytesRec = sender.Receive(bytes);
Console.WriteLine("Echoed test = {0}",
Encoding.ASCII.GetString(bytes, 0, bytesRec));
}
} catch (ArgumentNullException ane) {
Console.WriteLine("ArgumentNullException : {0}", ane.ToString());
} catch (SocketException se) {
Console.WriteLine("SocketException : {0}", se.ToString());
} catch (Exception e) {
Console.WriteLine("Unexpected exception : {0}", e.ToString());
} finally {
sender.Shutdown(SocketShutdown.Both);
sender.Close();
}
}
}
My shallow understanding of finally blocks is that it will always execute. But it doesn't seem to be the case here.
SO, what did I do wrong here? Should I just catch the exception, close the client socket on the server side and just move on, ignoring it? But I would prefer if an exception were not thrown at all.