multithreading - Is it possible to make blocking java socket read non active waiting?

Question

I have an application that needs to have thousands of socket connections open and waiting for a message. The client is using java blocking socket read. That means that I will be able to have only N concurrent opened connection(based on the executor number of thread set) as all the N threads will be blocked on active wait (RUNNABLE state)

Is there a way to make those socket read to "wake up" the the thread when data is available (in the same fashion of NIO sockets)?

i.e. Current behaviour thread-pool (4 threads)

• socketRead0(..) - RUNNABLE
• socketRead0(..) - RUNNABLE
• socketRead0(..) - RUNNABLE
• socketRead0(..) - RUNNABLE

No more thread can execute

Desired Behaviour thread-pool (4 threads)

• socketRead0(..) - WAITING (parking)
• socketRead0(..) - WAITING (parking)
• socketRead0(..) - WAITING (parking)
• socketRead0(..) - WAITING (parking)
• socketRead0(..) - RUNNABLE (it is executing read and will return data)

This way another thread having a socket read where data is available can kick in and get executed whilst others are waiting

NOTE: I know this can be achieved with NIO but want to know how can this behaviour be transferred to legacy sync calls (if possible) Thank you

question from:https://stackoverflow.com/questions/65883402/is-it-possible-to-make-blocking-java-socket-read-non-active-waiting

Answer 1

The answer is NO. All method of java.net.SocketInputStream are blocking. InputStream.available() is not implemented and always return 0. Without NIO the only way is to use one thread per socket.