When your application requests input from stdin, a 'Standard input' window appears:
You can type your line of text into the window and then either press the Enter key on your keyboard or click the Enter button. By default, everything you type is echoed to the server’s output area. Clear the tick against Echo stdin to stdout to switch this off.
You can signal end of file by typing Ctrl+Z or clicking End of File.
Terminate Application both signals end of file to the application and stops the server from listening to it (see 
).
The window heading 'Standard input' can be changed from the Diamond application with the prompt function.