The parent might read the memory before the child has written the message.

Shared memory automatically clears its contents when a child process starts.

The parent must use recv() instead of a normal memory read.

Shared memory cannot be accessed by both parent and child processes.

pipe

Shared memory

FIFO

Message queues

Unix domain socket

Call recv() to wait for the first message.

Call accept() to send a connection request to the client.

Call connect() to establish a connection with a client.

Call listen() to put the socket into a listening state.

Both clients have sent complete messages.

The server has received all data from both clients.

Both client connections have been closed.

At least one monitored file descriptor has an event reported by poll().

The server cannot handle more than one client at a time.

The server wastes CPU time checking inactive clients and may delay responses by approximately 100 ms, plus processing time.

Non-blocking sockets do not allow the server to receive data.

The server must create a separate thread for each client.

poll() waits until all file descriptors are ready or the timeout expires.

poll() blocks until data is available to read from every file descriptor.

poll() checks each file descriptor sequentially and returns only when all have been checked.

poll() returns as soon as at least one file descriptor is ready, or the timeout expires.

pipe

Shared memory

FIFO

Message queue

Unix domain socket