Add port checking functionality and tests

pkg/connection/port.go

@@ -0,0 +1,33 @@
+package connection
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"strings"
+)
+
+// Check if the TCP port available on localhost
+func portAvailable(port int) bool {
+	conn, err := net.Dial("tcp", fmt.Sprintf("127.0.0.1:%v", port))
+
+	if err != nil {
+		if strings.Index(err.Error(), "connection refused") > 0 {
+			return true
+		}
+		return false
+	}
+
+	conn.Close()
+	return false
+}
+
+// Get available TCP port on localhost by trying available ports in a range
+func getAvailablePort(start int, limit int) (int, error) {
+	for i := start; i <= (start + limit); i++ {
+		if portAvailable(i) {
+			return i, nil
+		}
+	}
+	return -1, errors.New("No available port")
+}