Unfortunately, this is not easily possible at the current version.
The Rebex File Server is primary designed for file transfers. The shell support was added to support SCP protocol, its features are limited.
What you can only do is to implement your custom shell by overriding "sh" command. This of course means you have to implement all shell logic, but you receive every single character, so you can react to function keys. It can be done like this:
server.ShellCommand += (s, e) =>
{
// override "sh", which is default shell command
if (e.Command == "sh")
{
e.Action = (args, console) =>
{
while (true)
{
// read next character from the terminal console
var ch = console.ReadChar();
if (ch == null)
break;
// write character and it's code to terminal console
console.WriteLine("{0} ({1:X2})", ch < ' ' ? '?' : ch, (int)ch);
}
return 0;
};
}
};