CODEWITHSUNDEEP
c++multithreadingwinapiipc
Vikram Ranabhatt
Vikram Ranabhatt

Reputation: 7630

InterThread communication

I am working on client server application where I need to send the command read from the script file .

The format of the script file is as follows. 

CONNECT <www.abcd.com,80>
SEND :           AB 40 01 FF 00 00 00 09 01 01 07 00 00 C0 A8 01 87 AE 
MATCH<s,10>:     AB 40 01 FF 00 00 00 09 01 01 07 00 00 C0 A8 01 87 AE
SEND :       AB 34 01 FF00 00 00 0C 01 01 07 00 01 01 07 00 FF FF FF FF AE 
DISCONNECT
note: s in match is wait time in seconds.
here second byte is Msg ID.

When it encounter Match Command the Program should wait for match for specified second and then proceed to next command.

I have two thread running in the application

  1. Listener Thread- it will receive data from server.(select() is used here)
    it will be launched when the program encounter the connect command and goes off when
    encounter disconnect in config.
  2. main thread which will read command from the config file and execute.

Now when match is encounter main thread should send the match string to the Listener Thread for matching and wait there for signal from Listener Thread.

The Listener Thread will match the string with data received from the server if it matches it will single the event(SetEvent() windows) to main thread and then main thread will log "Match found" other wise if time is elasped then it will log as "Match not found"

I thought of having a global variable char* g_MatchString.The main thread will update this variable whenever there is match command and wait for event(windows event) to be singled and the wait time will be equal to match time.

I need input from you guys whether my approach is correct or not.

Upvotes: 0

Views: 471

Answers (2)

Carey Gregory
Carey Gregory

Reputation: 6846

Don't use a global. That just creates the potential for race conditions when someone adds complexity in the future. The match string should be passed to the thread as an input argument. You don't say how you're launching the thread, but if you're using _beginthread() you simply allocate a buffer and pass it to _beginthread() in the arglist parameter. When the listener thread terminates, the main thread can safely free the match string buffer. This keeps it nicely self-contained and free of potential race conditions if additional threads are ever added. If you're launching the thread with CreateThread(), you would pass it via the lpParameter parameter.

Other than the global, I think your approach is sound.

Upvotes: 1

Remy Lebeau
Remy Lebeau

Reputation: 598124

Since the main thread is waiting on the listener thread, and the listener thread's sole purpose is to read inbound data, I would suggest just getting rid of the listener thread altogether and let the main thread do the reading directly.

Upvotes: 0

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