Zero is a valid value for SessionOptions.PortNumber

Source commit: 6226efd24cda7d15d4c37d43a1a93d8f7f50319f

dotnet/SessionOptions.cs

@@ -401,9 +401,9 @@ namespace WinSCP
 
         private void SetPortNumber(int value)
         {
-            if ((value < 1) || (value > 65535))
+            if ((value < 0) || (value > 65535))
             {
-                throw new ArgumentException("Port number has to be in range from 0 to 65535");
+                throw new ArgumentOutOfRangeException("Port number has to be in range from 0 to 65535");
             }
 
             _portNumber = value;