Support Windows SO_REUSEADDR (#822)

* Support Windows SO_REUSEADDR

* Update the comment

* Renew comment of the Listen method on Windows

3 files changed, 15 insertions, 23 deletions

diff --git a/reuseport/reuseport_test.go b/reuseport/reuseport_test.go
index 76df6ee..a9b60ea 100644
--- a/reuseport/reuseport_test.go
+++ b/reuseport/reuseport_test.go
@@ -1,5 +1,3 @@
-// +build !windows
-
 package reuseport
 
 import (
diff --git a/reuseport/reuseport_windows.go b/reuseport/reuseport_windows.go
index 8137eb5..bf5c312 100644
--- a/reuseport/reuseport_windows.go
+++ b/reuseport/reuseport_windows.go
@@ -1,11 +1,23 @@
 package reuseport
 
 import (
-	"fmt"
+	"context"
 	"net"
+	"syscall"
+
+	"golang.org/x/sys/windows"
 )
 
-// Listen always returns ErrNoReusePort on Windows
+var listenConfig = net.ListenConfig{
+	Control: func(network, address string, c syscall.RawConn) (err error) {
+		return c.Control(func(fd uintptr) {
+			err = windows.SetsockoptInt(windows.Handle(fd), windows.SOL_SOCKET, windows.SO_REUSEADDR, 1)
+		})
+	},
+}
+
+// Listen returns TCP listener with SO_REUSEADDR option set, SO_REUSEPORT is not supported on Windows, so it uses
+// SO_REUSEADDR as an alternative to achieve the same effect.
 func Listen(network, addr string) (net.Listener, error) {
-	return nil, &ErrNoReusePort{fmt.Errorf("Not supported on Windows")}
+	return listenConfig.Listen(context.Background(), network, addr)
 }
diff --git a/reuseport/reuseport_windows_test.go b/reuseport/reuseport_windows_test.go
deleted file mode 100644
index 33ac337..0000000
--- a/reuseport/reuseport_windows_test.go
+++ /dev/null
@@ -1,18 +0,0 @@
-// +build windows
-
-package reuseport
-
-import (
-	"testing"
-)
-
-func TestListen(t *testing.T) {
-	_, err := Listen("tcp6", "[::1]:10082")
-	if err == nil {
-		t.Fatalf("unexpected non-error creating listener")
-	}
-
-	if _, errnoreuseport := err.(*ErrNoReusePort); !errnoreuseport {
-		t.Fatalf("unexpected error creating listener: %s", err)
-	}
-}