Send data from Python to C#

I'm trying to send data from a python script to my c# application using a standard input stream. I also need to eventually send data back from my c# application to the another python script. I first tried to do this with a UDP Connection which works fine for a couple lines, but I have a fair amount of data to send (a few thousand lines) and a requirement for data integrity which UDP cannot provide. I could also write to a file, but that seems very inefficient.

One last restriction is that while my two applications are related I cannot setup a direct connection between them using something like IronPython as they are both spawned separately by a 3rd party application.

This is what I am currently trying, but it is not working. Similar to this question: Passing data between Python and C# without writing a file

p = subprocess.Popen(C_SHARP_EXECUTABLE_FILE_PATH, stdout=subprocess.PIPE, stdin=subprocess.PIPE, stderr=subprocess.PIPE)
p.communicate(blob)

On my C# side I'm not entirely sure how to read this data, but I've tried using things like a loop around this:

Console.ReadLine()

or getting the standard input and reading from it directly using:

Console.OpenStandardInput();

The current issue is that as soon as I call p.communicate my Python script gets locked and doesn't proceed. If it's waiting for the line to be read, what do I need to do to make it stop waiting? I tried only providing the stdin parameter, but that didn't help.