Machine Problem 5: The Data Server Moved Out! Solution

Introduction

In this machine problem we improve the request channel to provide communication across the network. Speci cally, we allow the the client-side end of a request channel to reside on one machine, and the server-side end of the channel on another machine. The communication over a request channel is to be provided by a single TCP connection.

In order to establish request channels over the network, the interface of the request channel must be modi ed somewhat. Below is a de nition of the NetworkRequestChannel class that supports request channels across machine boundaries:


NetworkRequestChannel(const string _server_host_name, const unsigned short _port_no); /* Creates a CLIENT-SIDE local copy of the channel. The channel is connected

to the given port number at the given server host.

THIS CONSTRUCTOR IS CALLED BY THE CLIENT. */

NetworkRequestChannel(const unsigned short _port_no,

void * (*connection_handler) (int *));

/*    Creates a SERVER-SIDE local copy of the channel that is accepting connections at the given port number.

NOTE that multiple clients can be connected to the same server-side end of the request channel. Whenever a new connection comes in, it is accepted by the the server, and the given connection handler is invoked. The parameter to the connection handler is the file descriptor of the slave socket returned by the accept call.

NOTE that the connection handler does not want to deal with closing the socket. You will have to close the socket once the connection handler is done. */

~NetworkRequestChannel();

/* Destructor of the local copy of the channel. */

string send_request(string _request);

/* Send a string over the channel and wait for a reply. */

string cread();

/*    Blocking read of data from the channel. Returns a string of characters read from the channel. Returns NULL if read failed. */

int cwrite(string _msg);

/*    Write the data to the channel. The function returns the number of characters written to the channel. */

You are to modify the data server program from MP3/MP4 to handle incoming requests over network request channels instead of request channels. The data server must be able to handle


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multiple request channels, either from the same client or from di erent clients, possibly on di erent machines.

You also have to modify the client from MP4 to send requests over network request channels.1 Use the same source code of the data server as in MP3 or MP4 (in le dataserver.C) to compile and then to execute as part of your program (i.e. in a separate process).

The Assignment

You are to write a program (call it client.C) that consist of a number of request threads, one for each person, a number of worker threads, and a number of statistics threads, one for each person. The number of persons is xed to three in this MP (Joe Smith, Jane Smith, and John Doe). The number of data requests per person and the number of worker threads are to be passed as arguments to the invocation of the client program. As explained earlier, the request threads generate the requests and deposit them into a bounded bu er. The size of this bu er is passed as an argument to the client program.

Design your dataserver so that multiple instances of the client program, either from the same or from di erent client machines, can connect to the dataserver simultaneously. The client program is to be called in the following form:

client    -n <number of data requests per person> -b <size of bounded buffer in requests> -w <number of request channels>

-h <name of server host>

-p <port number of server host>

The data server is to be called in the following form:

dataserver    -p <port number for data server> -b <backlog of the server socket>

What to Hand In

You are to hand in one ZIP le, called <FIRSTNAME LASTNAME MP#>.zip, which contains a directory called <FIRSTNAME LASTNAME MP#>.

For this machine problem, Jane Student would submit one ZIP le, called JANE STUDENT MP5.zip, which contains a folder called JANE STUDENT MP5.

This directory contains all needed les for the TA to compile and run your program. (The expectation is that the TA, after typing make, will get two fully operational programs, one called client and the other dataserver, which then can be tested.) The directory should contain at least the following les:

{ Your implementation of the Network Request Channel, to be submitted in two les: NetworkRequestChannel.H and NetworkRequestChannel.C.

{ The updated client, with name client.C.

{ The updated data server, with name dataserver.C.


1You can use the client code from MP3 if you did not get MP4 to run. Clearly state this in your documentation and your report! Otherwise the TA will hate you.


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{ Any other le that is needed to compile and test your solution, including the updated makefile.

Submit a report, called report.pdf, which you include as part of the submission directory. In this report you present a brief performance evaluation of the system with varying numbers clients and sizes of the backlog bu er on the server.


























































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