BasicStdioExample.cs

using System;

namespace StdioComms
{
	class Program
	{
		public static void Main(string[] args)
		{
			if (args.Length > 0 && args[0] == "client")
			{
				// client
				
				string line;
				
				while ((line = Console.ReadLine()) != null)
				{
					Console.WriteLine(int.Parse(line) * 2);
				}
			}
			else
			{
				// controller
				
				string line;
				
				var procStart = new System.Diagnostics.ProcessStartInfo("stdioComms.exe");
				procStart.RedirectStandardInput = true;
				procStart.RedirectStandardOutput = true;
				procStart.Arguments = "client";
				procStart.UseShellExecute = false;
				var proc = System.Diagnostics.Process.Start(procStart);
				
				var procWriter = proc.StandardInput;
				var procReader = proc.StandardOutput;
				
				while ((line = Console.ReadLine()) != null)
				{
					procWriter.WriteLine(line);
					Console.WriteLine(procReader.ReadLine());
				}
				
				proc.Kill();
			}
		}
	}
}

When run, it spawns a new client process, which it then passes input to, and writes output from, synchronously. The effect is that you have a unnecessarily complicated terminal which doubles any integer you plug in.