How do I send data from another program?

Hello Epic Games!!
I making online game that purpose to study network.
I developed lobby program with C#.
And when game execute, I want to send user information to an Unreal game.
I’m curious that how send data to Unreal game.

↓↓↓Part of C# code for game execution.(its pseudo code)↓↓↓

. . . . .
GameExecuteButtonClick()

{
. . .

Process.Start("UnrealGame.exe",parameter)
//How to code part of parameter?
//If sending is successful, How to handle this data in UnrealGame?

. . .

}
. . . . .

↓↓↓Send Data↓↓↓

string hostname

string hostIP

string username1, username2, . . . .

p.s: I’m sorry that I don’t have enough English skill…

I am working on the same problem and would be very interested in a solution. I think answer is custom launch properties / variables but I don’t yet know if that is possible.
These links might provide some answers.

https://docs.unrealengine.com/en-us/Programming/Basics/CommandLineArguments

Thank you for your feedback

Found the answer and working on trying the implementation now: