Browsers do not allow direct port scanning for security reasons. Real network scanning requires desktop tools or authorized server-based services. In this section you will learn scanning concepts, common ports and safe usage principles.
Scan responsibly
Only scan networks you own or have permission to test. Unauthorized scanning may be illegal.
- Get written permission before scanning any network you do not own.
- Close or firewall ports for services you do not use.
- Scan again after changes to confirm nothing new is exposed.
Learn
Core concepts
Host discovery
Finds which devices are alive on a network, typically with ARP requests on a LAN or ICMP ping across networks.
Port scanning
Checks which TCP or UDP ports on a host accept connections. Each open port usually means a running service.
Service detection
Identifies what is listening on an open port, such as a web server, SSH or a database, and often its version.
Why not in the browser?
Browsers block raw sockets and access to local devices for security, so real scans need a desktop app or an authorized server.
How a scan works
Define the scope
Choose the address range or hosts you are authorized to test, for example 192.168.1.0/24.
Probe
The scanner sends lightweight requests and records which hosts answer and which ports respond.
Interpret
Results are mapped to devices and services so you can spot unknown hardware or unnecessary exposure.
Common ports
Well-known ports and the services that usually run on them.
FTP (data)
FTP
SSH
SMTP
DNS
HTTP
POP3
IMAP
HTTPS
MySQL
RDP
HTTP-alt
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