main（）和thread（）之间的通信

Question

I have a question about threads communication. there is client and server.

server:

1. main function- its job is to listen to some port (TCP communication) and get commands from the client
2. the thread job is to transmit video fluently to the client.

client:

1. main function- transmit commands to server
2. thread- watch the video

the TCP\\video part works fine. after the main function of the server, got the command from the client, I need to send the command to the video thread and send back from the video thread to the server's main- "ok" .

the problem is to send commands from the server's main, to the video thread and vice versa.

its enough that the command will be one variable..

any ideas? thanks!

Answer 1

The pipe is a bad approach towards two way communication, you could use, shared memory. In shared memory, both processes have access to some memory that can be used read or write, such that writes in one are visible in the reads of the other and vice versa.

for more details on shared memory http://www.cs.cf.ac.uk/Dave/C/node27.html

Answer 2

if threads and one variable then use atomic variable. if object then use locking (trylock inside video streaming loop and lock write command inside main). if you want commands as queue-ed then use safe concurent queue

I think on your case: I would do it with two Wait-free ring buffer from boost examples. Making two single producer -consumer.In one producer will be main function consumer other thread,on another one vice versa. (it be like using two pipes in unix but efficient one)

A wait-free ring buffer provides a mechanism for relaying objects from one single "producer" thread to one single "consumer" thread without any locks. The operations on this data structure are "wait-free" which means that each operation finishes within a constant number of steps. This makes this data structure suitable for use in hard real-time systems or for communication with interrupt/signal handlers.

Wait-free ring buffer

But considering that I am not aware of your situation there are might be more right ways.Maybe redesining at all