LAN Pinger
LAN Pinger is an Android App that scans a network for hosts and services. Currently it pings on TCP ports 7 (echo), 22 (ssh), 80 (http) and UPD port 53 (DNS). It also should use ICMP echo request (aka ping), but that's currently not possible due to a ↗Bug in Android.
![[Screenshot of LAN Pinger at startup, showing the first and last ip address to scan and the number of threads to use.]](screenshot1.png)
Startup
After startup, LAN Pinger shows its startup screen. The network selection will fill the fields for first address and last address with the first and last address of the network of the selected network interface. The update button allows the user update the list of available network interfaces in case the network settings have changed asynchronously. Instead of taking the first and last address to scan from the selection, it's also possible to enter them by hand. The default number of threads is 512. LAN Pinger will start as many threads as addresses to scan, but at most the specified maximum number. More threads means faster scan but also more resources. The last setting is the setting for SO_TIMEOUT. This is the milliseconds to wait for a response from a TCP port until LAN Pinger decides that the scanned address provides no service at the specified port.
LAN Pinger is überfast!
For a Samsung Galaxy S II GT-I9100, 256 threads are all easy. And a big number of threads helps a lot. While one thread is waiting for a network response, another thread can already send out the next LAN Pinger network request. With 256 threads and an SO_TIMEOUT setting of 500ms, which usually is more than sufficient for a LAN, LAN Pinger scans a typical class C network in less than 2 seconds!
![[Screenshot of LAN Pinger during a scan, showing the intermediate results in the background and the progress in foreground.]](screenshot2.png)
Scan Phase
While scanning, LAN Pinger shows a ProgressDialog that tells you how far the scan is. The secondary progress displays the percentage of host addresses which have already been tried to ping. The primary progress displays the percentage of host addresses which have been scanned completely. The intermediate scan results are already shown in the background.
![[Screenshot of LAN Pinger scan results, showing the found hosts and the discovered services.]](screenshot3.png)
Scan Results
After the scan, you can look at a table with the results. Each entry shows a host which has responded to LAN Pinger at least once, plus the services to which it was responding.
Future
My current plans for future versions are:
- Support network interfaces with multiple networks
- Let the user configure the ports to scan
- Allow favorites for scan and network settings
- Add an interface to dynamically discover and change the WLAN to scan
- Add a convenience interface to scan particular remote hosts
- Maybe make LAN Pinger available through the App Shop
