Working with Networking (net)
1. Creating TCP Server (net.createServer)
Example: Echo server
import net from "node:net" ; const server = net. createServer (( socket ) => { socket. write ( "hi \n " ); socket. pipe (socket); }); server. listen ( 7 , () => console. log ( "echo on 7" ));
2. Creating TCP Client
Example
const client = net. createConnection ({ port: 7 , host: "127.0.0.1" }, () => client. write ( "hello" )); client. on ( "data" , ( d ) => { console. log (d. toString ()); client. end (); });
3. Handling Connection Events
Event Fires connectionNew client (server) connectConnected (client) dataBytes received endFIN from peer closeFully closed errorSocket error timeoutIdle timeout reached
4. Writing Data to Socket (socket.write)
Behavior Detail Returns false Buffer full → wait for drain Encoding Default UTF-8 if string
5. Ending Connections (socket.end)
API Effect socket.end(data?)Half-close after sending socket.end()Send FIN
6. Destroying Sockets (socket.destroy)
Method Use socket.destroy(err?)Force close, optionally with error socket.destroyedBoolean flag
7. Getting Socket Address (socket.address)
Property Returns socket.address(){ address, family, port }socket.remoteAddress / remotePortPeer info socket.localAddress / localPortLocal info
8. Setting Socket Timeout (socket.setTimeout)
Example
socket. setTimeout ( 30_000 , () => socket. end ());
Note: Timeout fires after no activity; doesn't auto-close — handle in callback.
9. Implementing Keep-Alive (setKeepAlive)
API Use socket.setKeepAlive(true, ms)OS-level TCP keepalive socket.setNoDelay(true)Disable Nagle's algorithm
10. Using Unix Sockets
Pattern Code Server server.listen("/tmp/app.sock")Client net.createConnection({ path: "/tmp/app.sock" })
11. Handling Socket Errors
Code Meaning ECONNRESETPeer reset connection EPIPEWrote to closed socket EHOSTUNREACHRouting failure EADDRINUSEPort already bound