Made by and (C) Apoorv Kumar, 2012 IIT Guwahati
Released under GPL-V3
#UDP FS Query Client Server
In this utility , the client can send a file name to server and the server has to look it up , extract the last modification date and other details , and then report back to the client.
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I have standard ports both for client and server , known to each other.
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Each connection has a queue in which the requests are queued.
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After this the problem is reduced to CONSUMER-PRODUCER problem. Here the main thread is consumer of packets. While the connection thread is consumer.
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I have implemented the "waiting" of threads using a wait() call that is available to any object in Java.
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Threads are woken up using the notify_all() call that wakes up all threads waiting on an object (in this case the queue).
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To ensure that the queue is not edited by both consumer and producer at once , it uses a method of serialization called "sychronize()".
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Incase file is not found , the server marks DONE with status = 1. Marking an error.
###instructions to run the program compile the codes - -------------------------------- $ javac Server.java Client.java --------------------------------
1. run the server
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$ java Server
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2. run the client
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$ java Client localhost this_file
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###CLIENT OUTPUT IN THE IDEAL CASE =========================================================================== starting the client ... sending req to localhost request sent ... now waiting for reply ... a new connection id has been allocated: 3 ------------------------------------------------------ the file was located ... the last modification date of file is : Tue Jan 17 23:19:55 IST 2012 ------------------------------------------------------ sending DONE_ACK to localhost ===========================================================================
###SERVER OUTPUT IN THE IDEAL CASE =========================================================================== creating new connection for the client - /127.0.0.1 - id: 3 Producing this_file for: 3 ACK datagram sent Processing request from 3 found modification date of : this_file - Tue Jan 17 23:19:55 IST 2012 closing connection from client - /127.0.0.1 ===========================================================================
###Known Issues:
IN VERY VERY RARE CASES *DONE* PACKET REACHES BEFORE *ACK*
THE ACK PACKET IS DROPPED , WHILE THE CLIENT IS BUSY RECEIVING *DONE* .
IT ISN'T HANDLED IN THIS PROGRAM THOUGH ... THE CLIENT PROGRAM WAITS FOREVER.
ALSO NO *DONE_ACK* IS SENT FROM CLIENT SINCE IT IS JAMMED
CLIENT OUTPUT IN THIS CASE WOULD BE SOMETHING LIKE
===========================================================================
starting the client ...
sending req to localhost
request sent ...
now waiting for reply ...
------------------------------------------------------
the file was located ...
the last modification date of file is : Tue Jan 17 23:19:55 IST 2012
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__blinking cursor__
===========================================================================
THE RESULT IS RECEIVED CORRECTLY ... HOWEVER ...
PRESS CTRL+C TO END THE WAITING CLIENT.