From 8b39d6cc8221e1e3758d93d1fa30ca7837822445 Mon Sep 17 00:00:00 2001
From: Dan Buch <dan@meatballhat.com>
Date: Mon, 7 Jul 2025 21:23:01 -0400
Subject: [PATCH] Teensy TCP echo server

---
 tcp-challenge/server/cmd/server/main.go | 89 +++++++++++++++++++++++++
 tcp-challenge/server/go.mod             |  3 +
 2 files changed, 92 insertions(+)
 create mode 100644 tcp-challenge/server/cmd/server/main.go
 create mode 100644 tcp-challenge/server/go.mod

diff --git a/tcp-challenge/server/cmd/server/main.go b/tcp-challenge/server/cmd/server/main.go
new file mode 100644
index 0000000..723f5d1
--- /dev/null
+++ b/tcp-challenge/server/cmd/server/main.go
@@ -0,0 +1,89 @@
+package main
+
+import (
+	"context"
+	"io"
+	"log"
+	"net"
+	"os"
+	"os/signal"
+	"strconv"
+	"syscall"
+)
+
+func main() {
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+
+	addr := ":7765"
+	if len(os.Args) > 1 {
+		addr = os.Args[1]
+	}
+
+	poolSize := 10
+	if len(os.Args) > 2 {
+		if v, err := strconv.ParseInt(os.Args[2], 10, 64); err != nil {
+			log.Fatal(err)
+		} else {
+			poolSize = int(v)
+		}
+	}
+
+	log.Printf("listening at %v (workers=%v)", addr, poolSize)
+
+	listener, err := net.Listen("tcp", addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	workers := []*worker{}
+	requests := make(chan net.Conn)
+
+	for i := 0; i < poolSize; i++ {
+		w := &worker{id: i, r: requests}
+		go w.Start(ctx)
+		workers = append(workers, w)
+	}
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+			log.Println("accepting connection")
+			conn, err := listener.Accept()
+			if err != nil {
+				log.Printf("failed to accept connection: %v", err)
+				continue
+			}
+
+			log.Println("accepted connection")
+			requests <- conn
+		}
+	}
+}
+
+type worker struct {
+	id int
+	r  chan net.Conn
+}
+
+func (w *worker) Start(ctx context.Context) {
+	log.Printf("[worker %v] starting loop", w.id)
+
+	for {
+		select {
+		case <-ctx.Done():
+			log.Printf("[worker %v] exiting", w.id)
+			return
+		case conn := <-w.r:
+			log.Printf("[worker %v] handling connection", w.id)
+
+			io.Copy(conn, conn)
+
+			if err := conn.Close(); err != nil {
+				log.Printf("[worker %v] failed to echo: %v", w.id, err)
+			}
+		}
+	}
+}
diff --git a/tcp-challenge/server/go.mod b/tcp-challenge/server/go.mod
new file mode 100644
index 0000000..512d12f
--- /dev/null
+++ b/tcp-challenge/server/go.mod
@@ -0,0 +1,3 @@
+module git.meatballhat.com/x/box-o-sand/tcp-challenge/server
+
+go 1.21.4