A free app for Android, by First Row.

Network Scanner is a utility for scanning the Internet for you. You can search for hosts in your home network or in the selected IP range.

You can select to scan either the whole home network or a specific subnet. The first mode is useful if you want to find all devices that are using your WiFi and learn more about every device. The second mode is useful if you want to find a server of needed service in the selected network. The third mode is useful for professional tasks. You can select to use the first or second mode.