Studying Interprocess Communication

Today I had to solve a simple problem. Let's say there are two processes running on one computer. The first service polls a database for print jobs. As soon as a job is found, a second service has to send the job to the printer. So, effectively, I have to pass some data from one local service to another.

The first, "amateurish" solution that came to my mind was to write data to a text file by the "polling" service and read from that file by "printing" service. But I thought that the task like this should be a standard one and looked around. Here's one of the examples I found:

.NET 3.5 Adds Named Pipes Support

Here's the probably the simplest working example: First, I need to create two windows services. I add a timer to each service. I also add an event log to each of the services to be able to check if they work. One of the services will be a "server". Here's what goes into it's timer_Elapsed:

using (NamedPipeServerStream pipeServer = new NamedPipeServerStream("testPipe", PipeDirection.Out))
{
 pipeServer.WaitForConnection();

 try
 {
  using (StreamWriter sw = new StreamWriter(pipeServer))
  {
   sw.AutoFlush = true;
   string dt = DateTime.Now.ToString();
   sw.WriteLine(dt);
   pollingEventLog.WriteEntry(dt + " written by the server");
  }
 }
 catch (IOException ex)
 {
  pollingEventLog.WriteEntry(ex.Message);
 }
}

The other service will be a "client". Here's what goes into it's timer_Elapsed:

using (NamedPipeClientStream pipeClient = new NamedPipeClientStream(".", "testPipe", PipeDirection.In))
{
 pipeClient.Connect();
 using (StreamReader sr = new StreamReader(pipeClient))
 {
  string temp;
  while ((temp = sr.ReadLine()) != null)
  {
   printManagerEventLog.WriteEntry(temp + " read by the client");
  }
 }
}

This is it - after both services are compiled, installed and started, their cooperation can be observed through the Event Log. Total time including googling, understanding the concept and implementing the working example - under 30 minutes.

by Evgeny. Also posted on my website