Is there a way to conect the input/output of a console application to the output/input of another program - input

Question

I have an application i cannot edit that reads from the console and writes to it and i want to know how i can read what the program is saying and write back commands to the program.
This is for a minecraft server where i want to read what the players are saying and run commands acoording to what is said. (the server is the application i cannot edit)
I cannot create a modification for the server, because i am using a mod that checks if there are any other modifications done to the files and fails to load if that is the case.

Answer 1

I wrote a simple app in c# to get started with, to redirect the I/O streams you need to start the application (in this case the server) within your own application.
First we create a new instance of the System.Diagnostics.Process class
var process = new Process();
then we specify the start info
process.StartInfo = new ProcessStartInfo
{
FileName = Console.ReadLine(), //Reads executable path from console
RedirectStandardOutput = true,
RedirectStandardInput = true,
UseShellExecute = false
};
then we add an event handler, in this example it's just writes the lines with a "> " prefix
process.OutputDataReceived += (object sender, DataReceivedEventArgs e) => Console.WriteLine($"> {e.Data}");
and now we can start the process by calling Process#Start()
process.Start();
and finally we can call Process#BeginOutputReadLine() without this the OutputDataReceived event will never trigger
process.BeginOutputReadLine();
To send commands you can use the process' StandardInput stream
process.StandardInput.WriteLine("command");
The fully working code with example output (tested with cmd.exe, but it's must work with MC servers)
Code:
static void Main(string[] args)
{
Console.Write("Enter executable path: ");
var process = new Process();
process.StartInfo = new ProcessStartInfo
{
FileName = Console.ReadLine(), //Reads executable path, for example cmd is the input
RedirectStandardOutput = true,
RedirectStandardInput = true,
UseShellExecute = false
};
process.OutputDataReceived += (object sender, DataReceivedEventArgs e) => Console.WriteLine($"> {e.Data}");
process.Start();
process.BeginOutputReadLine();
process.StandardInput.WriteLine("echo a");
//Prevent closing
Console.ReadKey();
}
Output:
Enter executable path: cmd
> Microsoft Windows [Version 10.0.18362.239]
> (c) 2019 Microsoft Corporation. Minden jog fenntartva.
>
> F:\VisualStudio\StackOverflow\StackOverflow\bin\Debug\netcoreapp2.1>echo a
> a
>