From a402c2955017cd2c9432a9abaa086dac521adb00 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=2C=20S=C3=B6lver?= <henrik.solver@volvocars.com>
Date: Fri, 5 Aug 2022 19:52:12 +0200
Subject: [PATCH] First commit

---
 README.md |  8 +++++++
 go.mod    |  3 +++
 main.go   | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+)
 create mode 100644 README.md
 create mode 100644 go.mod
 create mode 100644 main.go

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..3cd8f69
--- /dev/null
+++ b/README.md
@@ -0,0 +1,8 @@
+# UDP receiver
+Just a small example how server receiving UDP packets can be implemented in Go.
+
+To send to it `nc` can be used
+
+`echo -n "some string" | nc -4 -u -w 0 localhost 30000`
+
+Sending `stop` will make the program exit.
\ No newline at end of file
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..98fc352
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module receievr
+
+go 1.18
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..1d46e58
--- /dev/null
+++ b/main.go
@@ -0,0 +1,62 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+)
+
+func main() {
+	var wg sync.WaitGroup
+	conn, err := net.ListenUDP("udp4", &net.UDPAddr{Port: 30000})
+	if err != nil {
+		panic(err)
+	}
+	fmt.Printf("Listening on %v\n", conn.LocalAddr().String())
+	wg.Add(1)
+	inchan := make(chan string)
+	t := time.NewTimer(time.Minute)
+	go readProc(&wg, conn, inchan)
+loop:
+	for {
+		select {
+		case s := <-inchan:
+			fmt.Printf("got %s\n", s)
+			if s == "stop" {
+				fmt.Println("stop stop", s)
+				conn.Close()
+				break loop
+			}
+		case timeStamp := <-t.C:
+			conn.Close()
+			fmt.Printf("Time Stop %v\n", timeStamp)
+			break loop
+		}
+	}
+	fmt.Println("Exiting")
+	wg.Wait()
+
+}
+
+func readProc(wg *sync.WaitGroup, conn *net.UDPConn, inchan chan string) {
+	defer wg.Done()
+	var n int
+	var addr *net.UDPAddr
+	var err error
+	for {
+		buf := make([]byte, 1000)
+		n, addr, err = conn.ReadFromUDP(buf)
+		if err != nil {
+			if errors.Is(err, net.ErrClosed) {
+				fmt.Println("Socket closed")
+			} else {
+				fmt.Printf("Got some other error: %v\n", err.Error())
+			}
+			return
+		}
+		fmt.Printf("Received %v bytes from %v\n", n, addr.String())
+		inchan <- string(buf[:n])
+	}
+}