Network Tools

Port Checker

Check whether specific ports on a host are open.

ℹ️Due to browser security restrictions, port detection is implemented through HTTP/WebSocket connection attempts, and results may not be completely accurate. Only ports supporting HTTP/HTTPS or WebSocket protocols can be detected. For precise detection, please use system-level tools like nmap.
📋 Common Ports Reference
21FTPFile Transfer Protocol
22SSHSecure Shell
23TelnetTelnet Protocol
25SMTPSimple Mail Transfer Protocol
53DNSDomain Name System
80HTTPHypertext Transfer Protocol
110POP3Post Office Protocol v3
143IMAPInternet Message Access Protocol
443HTTPSHTTP Secure
465SMTPSSMTP Secure
587SMTPMail Submission
993IMAPSIMAP Secure
995POP3SPOP3 Secure
1433MSSQLSQL Server Database
1521OracleOracle Database
3306MySQLMySQL Database
3389RDPRemote Desktop Protocol
5432PostgreSQLPostgreSQL Database
5900VNCVirtual Network Computing
6379RedisRedis Database
8080HTTP-AltHTTP Alternate Port
8443HTTPS-AltHTTPS Alternate Port
27017MongoDBMongoDB Database

What is Port Checker?

Port checker tests whether specific network ports are open on a host, useful for firewall and service verification.

Common Ports

  • 21 - FTP
  • 22 - SSH
  • 80 - HTTP
  • 443 - HTTPS
  • 3306 - MySQL
  • 5432 - PostgreSQL

Use Cases

  • Firewall testing
  • Service availability check
  • Network troubleshooting

Frequently Asked Questions

The port shows closed — is my config wrong?
Check in order of likelihood: nothing listening (verify with ss -tlnp), cloud security group blocking, OS firewall (iptables/nftables — a separate gate from the cloud group), the provider blocking inbound (residential lines commonly block 25/80/443), or the service bound to 127.0.0.1 instead of 0.0.0.0. Eliminate layer by layer.
Is an open port dangerous?
Open is not automatically risky — the risk lives in what answers: an SSH on port 22 with a weak password and a patched nginx are different threat levels. Principle: close what you do not use; put access controls (allowlists, fail2ban, strong auth) on what you must.
Is this TCP or UDP checking?
TCP detection completes a handshake — reliable. UDP is connectionless: silence can mean open or dropped packets, so results are only "probably open / no response". For UDP services like DNS (53/UDP), verify with a protocol-native tool instead.