Merge pull request #2 from akutz/feature/tcp-ports

TCPPort Helper Funcs

.travis.yml

@@ -4,10 +4,11 @@ go:
 before_install:
   - go get github.com/axw/gocov/gocov
   - go get github.com/mattn/goveralls
-  - if ! go get code.google.com/p/go.tools/cmd/cover; then go get golang.org/x/tools/cmd/cover; fi
+  - go get golang.org/x/tools/cmd/cover
   - go get github.com/Masterminds/glide
 install:
-  - glide up
+  - glide up --resolve-current
+  - go get -t $(glide nv)
 script:
   - go install $(glide nv)
   - goveralls -service=travis-ci

glide.yaml

@@ -9,6 +9,5 @@ import:
     repo:    https://github.com/kardianos/osext.git
     vcs:     git
   - package: github.com/stretchr/testify
-    ref:     feature/glide
-    repo:    https://github.com/akutz/testify.git
+    repo:    https://github.com/stretchr/testify.git
     vcs:     git

gotil.go

@@ -280,3 +280,40 @@ func HomeDir() string {
 	homeDirSet = true
 	return homeDir
 }
+
+const (
+	minTCPPort         = 0
+	maxTCPPort         = 65535
+	maxReservedTCPPort = 1024
+	maxRandTCPPort     = maxTCPPort - (maxReservedTCPPort + 1)
+)
+
+var (
+	tcpPortRand = rand.New(rand.NewSource(time.Now().UnixNano()))
+)
+
+// IsTCPPortAvailable returns a flag indicating whether or not a TCP port is
+// available.
+func IsTCPPortAvailable(port int) bool {
+	if port < minTCPPort || port > maxTCPPort {
+		return false
+	}
+	conn, err := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%d", port))
+	if err != nil {
+		return false
+	}
+	conn.Close()
+	return true
+}
+
+// RandomTCPPort gets a free, random TCP port between 1025-65535. If no free
+// ports are available -1 is returned.
+func RandomTCPPort() int {
+	for i := maxReservedTCPPort; i < maxTCPPort; i++ {
+		p := tcpPortRand.Intn(maxRandTCPPort) + maxReservedTCPPort + 1
+		if IsTCPPortAvailable(p) {
+			return p
+		}
+	}
+	return -1
+}

gotil_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"io/ioutil"
+	"net"
 	"os"
 	"strings"
 	"testing"
@@ -406,3 +407,29 @@ func TestWriteIndented(t *testing.T) {
 func TestHomeDir(t *testing.T) {
 	assert.NotEqual(t, "", HomeDir())
 }
+
+func TestRandomTCPPort(t *testing.T) {
+	p := RandomTCPPort()
+	addr := fmt.Sprintf("127.0.0.1:%d", p)
+	t.Logf("listening on addr %s", addr)
+	conn, err := net.Listen("tcp", addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	conn.Close()
+}
+
+func TestIsTCPPortAvailable(t *testing.T) {
+	p := RandomTCPPort()
+	addr := fmt.Sprintf("127.0.0.1:%d", p)
+	t.Logf("listening on addr %s", addr)
+	conn, err := net.Listen("tcp", addr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+	_, err2 := net.Listen("tcp", addr)
+	if err2 == nil {
+		t.Fatalf("addr should be in use %s", addr)
+	}
+}