CS 3733 Operating Systems

This assignment relies on the first four assignments. Make a new directory and copy your code from assignment 4 into it.

• Part I: Network communication (Due November 24, 1997)
  • Download the UICI library from /usr/local/courses/cs3733/pup/apB

  • Compile and run this code to make sure that the client can send to the server.

  • Rename the server runsimd.c. Modify the program so that it takes two command line arguments: a port number and the process limit. The server does the following in a loop:
    • Monitors the port for a connection request.
    • Accepts the connection request.
    • Makes the connection.
    • Reads a request from the connection.
    • Echoes the request to standard output.
    • Writes an acknowledgment to the connection.
    • Closes the connection.

    Make the following assumptions about the exchange:

    • Messages end in a # character.
    • Acknowledgments consist of a # character.
    • The connections use sockets as implemented in the UICI library.
    • The only valid messages are:
      • testsim arg1 arg2
      • getstatus
      Here the arguments to testsim should be separated by blanks.

  • Modify the client code so that it does the following until it detects an end-of-file on standard input.
    • Get a line from standard input.
    • Open a network connection to the server.
    • Write the line to the server through the network connection.
    • Read the return message from the network until a #.
    • Echo the entire message to standard output.
    • Close the network connection.

  • After you get your program working with the client and the server running on the same machine, you should be sure to test it with the client and server running on different machines.

  • Each of you will be assigned a set of port numbers so that there won't be communication conflicts.

  • You should also try to test your client and server with the clients and servers of others.

  • You should test your program with more than one client at the same time.

• Part II: runsim as a child (due December 1, 1997)
  • Modify runsim as follows:
    • runsim does not output the status when a child is terminated or stopped.
    • When runsim outputs the list in response to a SIGUSR1, it ends the output in a # followed by a carriage return.
    • When runsim forks a child to run the process, it echoes the child ID to standard output.

  • Insert code prior to the main loop of runsimd to do the following:
    • Create a pipe.
    • Fork a child.
    • Perform the appropriate redirections so that the standard input of the parent is connected to the standard output of the child and vice versa.
    • Have the child execvp the runsim program.

  • Modify the main loop of runsimd to read messages from the network and forward them as described below to runsim.
    • Assume that the only valid messages are:
      • testsim arg1 arg2 arg3....
      • getstatus
    • If the command read from the network connection is testsim:
      • Write the entire command (without the #) to standard output.
      • Read the child ID generated to run the command from standard input.
      • Echo the child ID followed by # to the network connection.
    • If the command read from the network connection is getstatus:
      • Send a SIGUSR1 signal to runsim.
      • Read the output list from standard input.
      • Echo the output list to the network connection.
    • If the command is not testsim or getstatus, output an error message to standard error and echo a # to the network connection.
    • When the server detects that the network connection is closed, return to listening for a connection.