Add simple send

Makefile

@@ -1,10 +1,21 @@
 .PHONY: build
 build: bin/cyn
 
+.PHONY: build-all
+build-all: bin/cyn bin/cyn-linux bin/cyn-mac bin/cyn-windows
+
 # Build for local
-bin/cyn: ./cmd/cyn/*.go ./pkg/listener/*.go
+bin/cyn: ./cmd/cyn/*.go ./pkg/listener/*.go ./pkg/sender/*.go
 	go build -o bin/cyn ./cmd/cyn/*.go
 
+# Build for other OSes
+bin/cyn-linux: ./cmd/cyn/*.go ./pkg/listener/*.go ./pkg/sender/*.go
+	CGO_ENABLED=0 GOOS=linux go build -o bin/cyn-linux ./cmd/cyn/*.go
+bin/cyn-mac: ./cmd/cyn/*.go ./pkg/listener/*.go ./pkg/sender/*.go
+	CGO_ENABLED=0 GOOS=darwin go build -o bin/cyn-mac ./cmd/cyn/*.go
+bin/cyn-windows: ./cmd/cyn/*.go ./pkg/listener/*.go ./pkg/sender/*.go
+	CGO_ENABLED=0 GOOS=windows go build -o bin/cyn-windows ./cmd/cyn/*.go
+
 .PHONY: docker
 docker:
 	docker build -t evertras/cyn:latest .

README.md

@@ -25,17 +25,26 @@ Config file for more advanced setups.
 
 ## How to use it
 
-For simple use cases, just use command line args.
+For simple use cases, just use command line args.  By convention, lowercase
+means listen while uppercase means send.
 
 ```bash
 # On Machine A - 192.168.58.2
-cyn --listen-udp 192.168.58.1:1234 --call-tcp 192.168.58.3:3456 --call-tcp 192.168.58.4:3456
+cyn --listen-udp 192.168.58.2:1234 --send-udp 192.168.58.3:3456 --send-udp 192.168.58.4:3456
 
 # On Machine B - 192.168.58.3 (shorthand flags)
-cyn -l 192.168.58.2:2345 -t 192.168.58.2:1234 -t 192.168.58.4:3456
+cyn -u 192.168.58.3:2345 -U 192.168.58.2:1234 -U 192.168.58.4:3456
 
-# On Machine C - 192.168.58.4 (broadcasting)
-cyn -l 192.168.58.3:3456 --broadcast 192.168.58.255
+# On Machine C - 192.168.58.4 (mixed)
+cyn -u 192.168.58.4:3456 --send-udp 192.168.58.2:2345
+```
+
+```bash
+# Listen for broadcast messages on Machine A
+cyn -u :1234
+
+# Broadcast messages from Machine B using the regular UDP sender
+cyn -U 192.168.58.255:1234
 ```
 
 ## Why the name

cmd/cyn/root.go

@@ -3,19 +3,23 @@ package main
 import (
 	"fmt"
 	"net"
+	"time"
 
 	"github.com/spf13/cobra"
 	"golang.org/x/sync/errgroup"
 
 	"github.com/evertras/cynomys/pkg/listener"
+	"github.com/evertras/cynomys/pkg/sender"
 )
 
 var (
 	listenOnUDPList []string
+	sendUDPToList   []string
 )
 
 func init() {
-	rootCmd.Flags().StringSliceVarP(&listenOnUDPList, "listen-udp", "l", nil, "An IP:port address to listen on for UDP.  Can be specified multiple times.")
+	rootCmd.Flags().StringSliceVarP(&listenOnUDPList, "listen-udp", "u", nil, "An IP:port address to listen on for UDP.  Can be specified multiple times.")
+	rootCmd.Flags().StringSliceVarP(&sendUDPToList, "send-udp", "U", nil, "An IP:port address to send to (UDP).  Can be specified multiple times.")
 }
 
 var rootCmd = &cobra.Command{
@@ -36,6 +40,26 @@ var rootCmd = &cobra.Command{
 			})
 		}
 
+		for _, sendUDPTo := range sendUDPToList {
+			addr, err := net.ResolveUDPAddr("udp", sendUDPTo)
+
+			if err != nil {
+				return fmt.Errorf("net.ResolveUDPAddr for %q: %w", sendUDPTo, err)
+			}
+
+			eg.Go(func() error {
+				c := sender.NewUDPSender(*addr)
+
+				for {
+					err := c.Send([]byte("hi"))
+					if err != nil {
+						return fmt.Errorf("c.Send: %w", err)
+					}
+					time.Sleep(time.Second)
+				}
+			})
+		}
+
 		return eg.Wait()
 	},
 }

go.mod

@@ -7,14 +7,3 @@ require (
 	github.com/spf13/cobra v1.1.1
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58
 )
-
-require (
-	github.com/cucumber/gherkin-go/v19 v19.0.3 // indirect
-	github.com/cucumber/messages-go/v16 v16.0.1 // indirect
-	github.com/gofrs/uuid v4.0.0+incompatible // indirect
-	github.com/hashicorp/go-immutable-radix v1.3.0 // indirect
-	github.com/hashicorp/go-memdb v1.3.0 // indirect
-	github.com/hashicorp/golang-lru v0.5.4 // indirect
-	github.com/inconshreveable/mousetrap v1.0.0 // indirect
-	github.com/spf13/pflag v1.0.5 // indirect
-)

go.sum

@@ -120,8 +120,10 @@ github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+o
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pretty v0.2.1 h1:Fmg33tUaq4/8ym9TJN1x7sLJnHVwhP33CNkpYV/7rwI=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/magiconair/properties v1.8.1/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mattn/go-colorable v0.0.9/go.mod h1:9vuHe8Xs5qXnSaW/c/ABM9alt+Vo+STaOChaDxuIBZU=
@@ -299,6 +301,7 @@ google.golang.org/grpc v1.21.1/go.mod h1:oYelfM1adQP15Ek0mdvEgi9Df8B9CZIaU1084ij
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/ini.v1 v1.51.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=

pkg/sender/udp.go

@@ -0,0 +1,37 @@
+package sender
+
+import (
+	"fmt"
+	"net"
+)
+
+type UDPSender struct {
+	broadcastAddr net.UDPAddr
+	conn          *net.UDPConn
+}
+
+func NewUDPSender(addr net.UDPAddr) *UDPSender {
+	return &UDPSender{
+		broadcastAddr: addr,
+	}
+}
+
+func (s *UDPSender) Send(data []byte) error {
+	if s.conn == nil {
+		c, err := net.DialUDP("udp4", nil, &s.broadcastAddr)
+
+		if err != nil {
+			return fmt.Errorf("net.DialUDP: %w", err)
+		}
+
+		s.conn = c
+	}
+
+	_, err := s.conn.Write(data)
+
+	if err != nil {
+		return fmt.Errorf("s.conn.Write: %w", err)
+	}
+
+	return nil
+}