This repository contains small, focused examples of TCP networking in C:

• Multiple-client echo servers implemented using:
  • select(2) → binary server-select
  • poll(2) → binary server-poll
  • epoll(7) → binary server-epoll
• Clients
  • client → single connection, sends multiple requests over one TCP connection
  • multiple-client → spins up multiple connections to the server and sends requests

Servers listen on 0.0.0.0:9090. Clients default to 127.0.0.1:9090.
The clients enable TCP keep-alive and read one response per request.

make                # builds: server-select, server-poll, server-epoll, client, multiple-client
make servers        # builds only the servers
make clients        # builds only the clients
make clean          # removes all built binaries

Optionally, you can also build the single-connection demo server:

make server-single  # builds 'server-single' (demo, not part of 'make all')

1. Start a server (pick one):

./server-select
# or:
./server-poll
# or:
./server-epoll

They listen on port 9090.

2. Run the single-connection client:

./client [server_ip] [port] [num_requests]
# defaults: 127.0.0.1 9090 3

Example:

./client 127.0.0.1 9090 5

3. Run the multi-connection client:

./multiple-client [server_ip] [port] [num_requests_per_client] [num_clients]
# defaults: 127.0.0.1 9090 3 10

Example:

./multiple-client 127.0.0.1 9090 2 20

4. (Optional) Single-connection demo server:

./server-single [port]
# defaults to port 9090 if omitted

• All code uses only POSIX/Linux sockets, no external libraries.
• The echo servers read from each client and write the same data back.
• Clients ignore SIGPIPE and handle SIGINT/SIGTERM for graceful shutdown.