Lesson 02 · Echo the bytes back - Build an HTTP Server

Echo the bytes back

A connection is a two-way pipe of bytes. Today you read what a client sends and write the same bytes back, giving you a running server you can actually talk to.

The goal

Read the bytes a client sends on a connection and write the identical bytes back.

Start here - the target

TO DO

Scenario: The server echoes what it receives

Givenan accepted connection

Whenthe client sends the bytes "ping"

Thenthe client reads back exactly "ping"

Background

A connection is just a stream of bytes in each direction. Read fills a buffer with whatever has arrived and tells you how many bytes that was; Write sends bytes the other way. Echoing means writing back exactly the slice you read — buf[:n], never the whole 1024-byte buffer.

This is your first runnable server. Wire handle into an accept loop and you can start it, connect with any TCP client, and watch your input bounce straight back. Every later lesson thickens this same read-then-write shape into real HTTP.

Make it work

func handle(conn net.Conn) {
    defer conn.Close()
    buf := make([]byte, 1024)
    n, _ := conn.Read(buf) // n = how many bytes actually arrived
    conn.Write(buf[:n])    // write back only those n bytes
}

CheckpointDONE

You have a running echo server - start it, connect, and see your bytes come back. Commit.