diff --git a/PinkConnection2-TestApp/PinkConnection2-TestApp/MainForm.cs b/PinkConnection2-TestApp/PinkConnection2-TestApp/MainForm.cs
index f893f7a..29338ee 100644
--- a/PinkConnection2-TestApp/PinkConnection2-TestApp/MainForm.cs
+++ b/PinkConnection2-TestApp/PinkConnection2-TestApp/MainForm.cs
@@ -79,6 +79,11 @@ namespace PinkConnection2_TestApp
 
 		void sendFrame()
 		{
+			if (port == null)
+			{
+				MessageBox.Show("Please select a serial port");
+				return;
+			}
 			byte byte1 = (byte)(64 | ((b & 8) | (b & 4) | (b & 2) | (b & 1)));
 			byte byte2 = (byte)(64 | (((b & 128) | (b & 64) | (b & 32) | (b & 16)) >> 4));
 			port.Write(((char)byte1).ToString());
@@ -89,7 +94,12 @@ namespace PinkConnection2_TestApp
 		{
 			if (CommandTextBox.Text.Length != 2)
 			{
-				MessageBox.Show("Command Length must not be less than 2");
+				MessageBox.Show("Command length must not be less than 2");
+				return;
+			}
+			if (port == null)
+			{
+				MessageBox.Show("Please select a serial port");
 				return;
 			}
 			port.Write(CommandTextBox.Text);