Task on POSIX message queues

Chat #

Write a server and a client for a simple chat using POSIX queues.
When the server starts, it opens a queue named "chat_{server_name}" where {server_name} is the only server argument. This queue is used for incoming communication from clients to the server.

The client starts with two arguments: {server_name} and {client_name}. It connects to the server using the server queue, opens its own queue "chat_{client_name}" for reading messages from the server, and sends all typed messages from standard input to the server.

There are three types of messages (use message priority to distinguish the type):

  • 0 - connection
  • 1 - disconnection
  • 2 - regular messages

The connection message sent to the server from the client contains its name. The disconnection message is an empty 1-byte message signaling client or server termination. Regular messages from clients contain raw messages sent as C-strings without any metadata. The server sends back to all clients messages formatted as: "[{sender_name}] {message}".

The server can also send its own messages typed from the standard input; in that case, the sender name is SERVER.

Use mq_notify for obtaining messages and information about the sender PID.

Stages: #

  1. The server opens queue "chat_{server_name}", reads from it, and displays in a loop a read message on the standard output as: "[{msg_prio}] {msg_content}".
    The client opens "chat_{server_name}" and sends its name there with the proper message priority.

  2. The client creates its queue "chat_{client_name}" at the start.
    The server opens a client’s queue after receiving the client’s name (sent as a raw C-string with priority 0) and stores information about connected clients (max 8 clients connected at once).
    On a client connection, the server displays: "Client {client_name} has connected!" on the standard output.

  3. A client sends lines from the standard input to the server.
    The server receives data from clients using mq_notify. It displays them on the standard output formatted as: "[{sender_name}] {message}" and broadcasts them to all clients in the same format.
    The server also supports typing messages, which are sent with SERVER as the sender name.
    Clients receive messages from the server and display them as: "[{client_name}] {message}".

  4. The server supports closing on Ctrl-C. It sends information about its closing using an “empty” message with the proper priority.
    Upon receiving the server closing message, clients display: "Server closed the connection" and terminate.
    Upon receiving the client closing message, the server displays: "Client {client_name} disconnected!".
    All resources are correctly released – queues are closed and removed by their creators.