CS 3733 Operating Systems

• Reorganize your server application so that the parent forks a separate child to handle each direction of communication. In a loop the server should do:
  • Listen for a connection request.
  • Open the audio device.
  • Fork child 1 to do the play_open_file.
  • Fork child 2 to do the record_from_open_file.
  • Close the communfd.
  • Wait for the children to finish.
  • Close the audio device.

• Reorganize your client so that the parent forks a separate child to handle each direction of communication. The client should:
  • Make a connection request.
  • Open the audio device.
  • Fork child 1 to do the play_open_file.
  • Fork child 2 to do the record_from_open_file.
  • Close the communfd.
  • Wait for the children to finish.
  • Close the audio device.
  • Exit.

Part II: Graceful Shutdown and Resumption - Due April 24, 1998

• Make a new subdirectory and copy your working programs from Part I into it.
• Add the global static variables child1_ID and child2_ID to the server. Modify the server code so that when the parent forks each child it stores the PIDs in these variables. (This is so that the signal handler can access these variables.)
• Add code to the SIGUSR1 signal handler in the server so that it will kill each child. (Use the kill system call with SIGTERM.)
• Modify the client code in a similar way.
• Send the SIGUSR1 signal (kill -USR1 pid) to the client from the shell and see if it quits.
• Send the SIGUSR1 signal (kill -USR1 pid) to the server from the shell and see if it terminates the communication session and resumes listening.

Part III: Helpers - Due in class on April 29 - testing starting at 8 am

In this part of the assignment you will make it easier for someone to contact your server.

• Make a new subdirectory and copy the code from Part II into it.
• Modify your server so that before it goes into the loop it creates the file myFilename.csaudio in your public_html directory. This file contains two lines. The first line is the name of the machine that the server is running on (use gethostname). The second line is the port number that the server is listening on.
• Modify your client so that before it no longer takes two command line arguments. Instead it reads the hostname and port number from standard input.
• Install your client as a helper function in your Netscape on the Sun network by following these directions.

  NOTE
  In order to get the helper to read the csaudio file, install the helper with the line:

  cat %s | /fullpath/client

  in the Application: box

• Put a link to http://ringer.cs.utsa.edu/yourname/myFilename.csaudio on your homepage.
• Start your server on one machine and run netscape on another. When you click on the above link, your client should start up and connect to your server.
• Test your program with other members of the class.