Add non-blocking IO support and improved exception handling in C# wrapper

examples/csharp/Socket.cs

@@ -13,7 +13,7 @@
 
 using System; // For ObjectDisposedException
 using System.Net; // For IPEndPoint
-using System.Net.Sockets; // For SocketException
+using System.Net.Sockets; // For ZeroTier.SocketException
 using System.Runtime.InteropServices;
 
 using ZeroTier;
@@ -23,16 +23,6 @@ using ZeroTier;
 /// </summary>
 namespace ZeroTier
 {
-	public class ZeroTierException : Exception
-	{
-		public ZeroTierException(int _serviceErrorCode, int _socketErrorCode) {
-			ServiceErrorCode = _serviceErrorCode;
-			SocketErrorCode = _socketErrorCode;
-		}
-		public int ServiceErrorCode { get; set; }
-		public int SocketErrorCode { get; set; }
-	}
-
 	/// <summary>
 	/// ZeroTier Socket - An lwIP socket mediated over a ZeroTier virtual link
 	/// </summary>
@@ -54,6 +44,7 @@ namespace ZeroTier
 		int _fd;
 		bool _isClosed;
 		bool _isListening;
+		bool _isBlocking;
 
 		AddressFamily _socketFamily;
 		SocketType _socketType;
@@ -62,6 +53,13 @@ namespace ZeroTier
 		internal EndPoint _localEndPoint;
 		internal EndPoint _remoteEndPoint;
 
+		private void InitializeInternalFlags()
+		{
+			_isClosed = false;
+			_isListening = false;
+			_isBlocking = false;
+		}
+
 		public Socket(AddressFamily addressFamily, SocketType socketType, ProtocolType protocolType)
 		{
 			int family = -1;
@@ -103,12 +101,12 @@ namespace ZeroTier
 			}
 			if ((_fd = zts_socket(family, type, protocol)) < 0)
 			{
-				throw new SocketException((int)_fd);
+				throw new ZeroTier.SocketException((int)_fd);
 			}
 			_socketFamily = addressFamily;
 			_socketType = socketType;
 			_socketProtocol = protocolType;
-			_isClosed = false;
+			InitializeInternalFlags();
 		}
 
 		private Socket(int fileDescriptor,
@@ -123,9 +121,8 @@ namespace ZeroTier
 			_socketProtocol = protocolType;
 			_localEndPoint = localEndPoint;
 			_remoteEndPoint = remoteEndPoint;
-			_isClosed = false;
-			_isListening = false;
 			_fd = fileDescriptor;
+			InitializeInternalFlags();
 		}
 
 		public void Connect(IPEndPoint remoteEndPoint)
@@ -135,7 +132,7 @@ namespace ZeroTier
 			}
 			if (_fd < 0) {
 				// Invalid file descriptor
-				throw new SocketException((int)Constants.ERR_SOCKET);
+				throw new ZeroTier.SocketException((int)Constants.ERR_SOCKET);
 			}
 			if (remoteEndPoint == null) {
 				throw new ArgumentNullException(nameof(remoteEndPoint));
@@ -182,7 +179,7 @@ namespace ZeroTier
 				*/
 			}
 			if (err < 0) {
-				throw new ZeroTierException(err, ZeroTier.Node.ErrNo);
+				throw new ZeroTier.SocketException(err, ZeroTier.Node.ErrNo);
 			}
 			_remoteEndPoint = remoteEndPoint;
 		}
@@ -194,7 +191,7 @@ namespace ZeroTier
 			}
 			if (_fd < 0) {
 				// Invalid file descriptor
-				throw new SocketException((int)Constants.ERR_SOCKET);
+				throw new ZeroTier.SocketException((int)Constants.ERR_SOCKET);
 			}
 			if (localEndPoint == null) {
 				throw new ArgumentNullException(nameof(localEndPoint));
@@ -239,7 +236,7 @@ namespace ZeroTier
 				*/
 			}
 			if (err < 0) {
-				throw new SocketException((int)err);
+				throw new ZeroTier.SocketException((int)err);
 			}
 			_localEndPoint = localEndPoint;
 		}
@@ -251,12 +248,12 @@ namespace ZeroTier
 			}
 			if (_fd < 0) {
 				// Invalid file descriptor
-				throw new SocketException((int)Constants.ERR_SOCKET);
+				throw new ZeroTier.SocketException((int)Constants.ERR_SOCKET);
 			}
 			int err = Constants.ERR_OK;
 			if ((err = zts_listen(_fd, backlog)) < 0) {
 				// Invalid backlog value perhaps?
-				throw new SocketException((int)Constants.ERR_SOCKET);
+				throw new ZeroTier.SocketException((int)Constants.ERR_SOCKET);
 			}
 			_isListening = true;
 		}
@@ -268,7 +265,7 @@ namespace ZeroTier
 			}
 			if (_fd < 0) {
 				// Invalid file descriptor
-				throw new SocketException((int)Constants.ERR_SOCKET);
+				throw new ZeroTier.SocketException((int)Constants.ERR_SOCKET);
 			}
 			if (_isListening == false) {
 				throw new InvalidOperationException("Socket is not in a listening state. Call Listen() first");
@@ -284,7 +281,7 @@ namespace ZeroTier
 
 			int err = zts_accept(_fd, remoteAddrPtr, addrlenPtr);
 			if (err < 0) {
-				throw new SocketException((int)err);
+				throw new ZeroTier.SocketException(err, ZeroTier.Node.ErrNo);
 			}
 			in4 = (zts_sockaddr_in)Marshal.PtrToStructure(remoteAddrPtr, typeof(zts_sockaddr_in));
 			// Convert sockaddr contents to IPEndPoint
@@ -340,13 +337,79 @@ namespace ZeroTier
 			}
 		}
 
+		public bool Blocking
+		{
+			get {
+				return _isBlocking;
+			}
+			set {
+				if (_isClosed) {
+					throw new ObjectDisposedException("Socket has been closed");
+				}
+				int opts = 0;
+				if ((opts = zts_fcntl(_fd, (int)(ZeroTier.Constants.F_GETFL), 0)) < 0) {
+					throw new ZeroTier.SocketException(opts, ZeroTier.Node.ErrNo);
+				}
+				Console.WriteLine("before.opts={0}", opts);
+				if (value) { // Blocking
+					opts = opts & (~(ZeroTier.Constants.O_NONBLOCK));
+				}
+				if (!value) { // Non-Blocking
+					opts = opts | (int)(ZeroTier.Constants.O_NONBLOCK);
+				}
+				Console.WriteLine("after.opts={0}", opts);
+				if ((opts = zts_fcntl(_fd, ZeroTier.Constants.F_SETFL, (int)opts)) < 0) {
+					throw new ZeroTier.SocketException(opts, ZeroTier.Node.ErrNo);
+				}
+				_isBlocking = value;
+			}
+		}
+
+		public bool Poll(int microSeconds, System.Net.Sockets.SelectMode mode)
+		{
+			if (_isClosed) {
+				throw new ObjectDisposedException("Socket has been closed");
+			}
+			zts_pollfd poll_set = new zts_pollfd();
+			poll_set.fd = _fd;
+			if (mode == SelectMode.SelectRead) {
+				poll_set.events = (short)((byte)ZeroTier.Constants.POLLIN);
+			}
+			if (mode == SelectMode.SelectWrite) {
+				poll_set.events = (short)((byte)ZeroTier.Constants.POLLOUT);
+			}
+			if (mode == SelectMode.SelectError) {
+				poll_set.events = (short)((byte)ZeroTier.Constants.POLLERR | (byte)ZeroTier.Constants.POLLNVAL);
+			}
+			IntPtr poll_fd_ptr = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(zts_pollfd)));
+			Marshal.StructureToPtr(poll_set, poll_fd_ptr, false);
+			int result = 0;
+			int timeout_ms = (microSeconds / 1000);
+			uint numfds = 1;
+			if ((result = zts_poll(poll_fd_ptr, numfds, timeout_ms)) < 0) {
+				throw new ZeroTier.SocketException(result, ZeroTier.Node.ErrNo);
+			}
+			poll_set = (zts_pollfd)Marshal.PtrToStructure(poll_fd_ptr, typeof(zts_pollfd));
+			if (result == 0) { return false; } // No events
+			if (mode == SelectMode.SelectRead) {
+				return ((byte)poll_set.revents & (byte)ZeroTier.Constants.POLLIN) != 0;
+			}
+			if (mode == SelectMode.SelectWrite) {
+				return ((byte)poll_set.revents & (byte)ZeroTier.Constants.POLLOUT) != 0;
+			}
+			if (mode == SelectMode.SelectError) {
+				return ((poll_set.revents & (byte)ZeroTier.Constants.POLLERR) != 0) || ((poll_set.revents & (byte)ZeroTier.Constants.POLLNVAL) != 0);
+			}
+			return false;
+		}
+
 		public Int32 Send(Byte[] buffer)
 		{
 			if (_isClosed) {
 				throw new ObjectDisposedException("Socket has been closed");
 			}
 			if (_fd < 0) {
-				throw new SocketException((int)ZeroTier.Constants.ERR_SOCKET);
+				throw new ZeroTier.SocketException((int)ZeroTier.Constants.ERR_SOCKET);
 			}
 			if (buffer == null) {
 				throw new ArgumentNullException(nameof(buffer));
@@ -362,7 +425,7 @@ namespace ZeroTier
 				throw new ObjectDisposedException("Socket has been closed");
 			}
 			if (_fd < 0) {
-				throw new SocketException((int)ZeroTier.Constants.ERR_SOCKET);
+				throw new ZeroTier.SocketException((int)ZeroTier.Constants.ERR_SOCKET);
 			}
 			if (buffer == null) {
 				throw new ArgumentNullException(nameof(buffer));
@@ -483,10 +546,7 @@ namespace ZeroTier
 		[DllImport("libzt", EntryPoint="CSharp_zts_errno_get")]
 		static extern int zts_errno_get();
 
-		/// <summary>
+		/// <value>The value of errno for the low-level socket layer</value>
-		/// Gets the value of errno from the unmanaged region
-		/// </summary>
-		/// <value></value>
 		public static int ErrNo {
 			get {
 				return zts_errno_get();
@@ -519,5 +579,13 @@ namespace ZeroTier
 			[MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)]
 			public char[] sin_zero; // SIN_ZERO_LEN
 		}
+
+		[StructLayout(LayoutKind.Sequential)]
+		struct zts_pollfd
+		{
+			public int fd;
+			public short events;
+			public short revents;
+		}
 	}
 }

examples/csharp/SocketException.cs

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c)2013-2020 ZeroTier, Inc.
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file in the project's root directory.
+ *
+ * Change Date: 2024-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2.0 of the Apache License.
+ */
+/****/
+
+using System;
+
+namespace ZeroTier
+{
+	/// <summary>Exception class for ZeroTier service and low-level socket errors</summary>
+	public class SocketException : Exception
+	{
+		public SocketException(int _serviceErrorCode)
+		: base(String.Format("ServiceErrorCode={0} (See Constants.cs for error code meanings)", _serviceErrorCode))
+		{
+			ServiceErrorCode = _serviceErrorCode;
+		}
+		public SocketException(int _serviceErrorCode, int _socketErrorCode)
+		: base(String.Format("ServiceErrorCode={0}, SocketErrorCode={1} (See Constants.cs for error code meanings)", _serviceErrorCode, _socketErrorCode))
+		{
+			ServiceErrorCode = _serviceErrorCode;
+			SocketErrorCode = _socketErrorCode;
+		}
+		/// <value>High-level service error code. See Constants.cs</value>
+		public int ServiceErrorCode { get; }
+
+		/// <value>Low-level socket error code. See Constants.cs</value>
+		public int SocketErrorCode { get; }
+	}
+}

examples/csharp/example.cs

@@ -87,11 +87,31 @@ public class ExampleApp {
 			while (true) {
 				Console.WriteLine("Waiting for a connection...");
 				// Program is suspended while waiting for an incoming connection.
-				Console.WriteLine("accepting...");
+				bool nonblocking = true;
-				ZeroTier.Socket handler = listener.Accept();
-				data = null;
 
-				Console.WriteLine("accepted connection from: " + handler.RemoteEndPoint.ToString());
+				ZeroTier.Socket handler;
+
+				if (nonblocking) { // Non-blocking style Accept() loop using Poll()
+					Console.WriteLine("Starting non-blocking Accept() loop...");
+					listener.Blocking = false;
+					// loop
+					int timeout = 1000000; // microseconds (1 second)
+					while (true) {
+						Console.WriteLine("Polling... (for data or incoming connections)");
+						if (listener.Poll(timeout, SelectMode.SelectRead)) {
+							Console.WriteLine("Detected event (SelectRead). Accepting...");
+							handler = listener.Accept();
+							break;
+						}
+						Thread.Sleep(1000);
+					}
+				}
+				else { // Blocking style
+					Console.WriteLine("Starting blocking Accept() call...");
+					handler = listener.Accept();
+				}
+				data = null;
+				Console.WriteLine("Accepted connection from: " + handler.RemoteEndPoint.ToString());
 
 				// An incoming connection needs to be processed.
 				while (true) {
@@ -112,7 +132,7 @@ public class ExampleApp {
 				handler.Close();
 			}
 
-		} catch (ZeroTier.ZeroTierException e) {
+		} catch (ZeroTier.SocketException e) {
 			Console.WriteLine(e);
 			Console.WriteLine("ServiveErrorCode={0} SocketErrorCode={1}", e.ServiceErrorCode, e.SocketErrorCode);
 		}
@@ -136,7 +156,6 @@ public class ExampleApp {
 
 			// Connect the socket to the remote endpoint. Catch any errors.
 			try {
-
 				Console.WriteLine("Socket connecting to {0}...",
 					remoteServerEndPoint.ToString());
 
@@ -162,9 +181,7 @@ public class ExampleApp {
 
 			} catch (ArgumentNullException ane) {
 				Console.WriteLine("ArgumentNullException : {0}",ane.ToString());
-			} catch (SocketException se) {
+			} catch (ZeroTier.SocketException e) {
-				Console.WriteLine("SocketException : {0}",se.ToString());
-			} catch (ZeroTier.ZeroTierException e) {
 				Console.WriteLine(e);
 				Console.WriteLine("ServiveErrorCode={0} SocketErrorCode={1}", e.ServiceErrorCode, e.SocketErrorCode);
 			}