Open Port Checker
Check if a port is open or closed on any host.
All ▼
| Port | Service | Protocol | Category | Description |
|---|---|---|---|---|
| 0 | Reserved | TCP/UDP | Other | Reserved port; not used for communication |
| 1 | TCPMUX | TCP | Other | TCP port service multiplexer |
| 7 | Echo | TCP/UDP | Other | Echo protocol — returns received data back to sender |
| 9 | Discard | TCP/UDP | Other | Discard protocol — silently discards all data received |
| 11 | Systat | TCP | Other | Active users service |
| 13 | Daytime | TCP/UDP | Other | Daytime protocol — returns current date and time |
| 17 | QOTD | TCP | Other | Quote of the Day protocol |
| 19 | Chargen | TCP/UDP | Other | Character generator protocol for testing |
| 20 | FTP Data | TCP | File Transfer | FTP data transfer channel for active mode connections |
| 21 | FTP Control | TCP | File Transfer | FTP command/control channel for login and commands |
| 22 | SSH | TCP | Remote Access | Secure Shell — encrypted remote login, file transfer (SCP/SFTP) |
| 23 | Telnet | TCP | Remote Access | Unencrypted remote terminal access (legacy, insecure) |
| 25 | SMTP | TCP | Simple Mail Transfer Protocol — sending and relaying email | |
| 37 | Time | TCP/UDP | Other | Time protocol — returns 32-bit time value |
| 42 | WINS | TCP/UDP | DNS & Directory | Windows Internet Name Service replication |
| 43 | WHOIS | TCP | DNS & Directory | WHOIS protocol — domain registration lookup |
| 49 | TACACS+ | TCP | Security | Terminal Access Controller Access-Control System Plus |
| 53 | DNS | TCP/UDP | DNS & Directory | Domain Name System — resolves domain names to IP addresses |
| 67 | DHCP Server | UDP | Other | Dynamic Host Configuration Protocol — server responses |
| 68 | DHCP Client | UDP | Other | Dynamic Host Configuration Protocol — client requests |
| 69 | TFTP | UDP | File Transfer | Trivial File Transfer Protocol — simple, unauthenticated |
| 70 | Gopher | TCP | Web | Gopher protocol — predecessor to the World Wide Web |
| 79 | Finger | TCP | Other | Finger protocol — user information lookup |
| 80 | HTTP | TCP | Web | Hypertext Transfer Protocol — standard web traffic |
| 88 | Kerberos | TCP/UDP | Security | Kerberos authentication system for network security |
| 102 | ISO-TSAP | TCP | Other | ISO Transport Service Access Point (Siemens S7) |
| 104 | DICOM | TCP | Other | Digital Imaging and Communications in Medicine |
| 109 | POP2 | TCP | Post Office Protocol version 2 (deprecated) | |
| 110 | POP3 | TCP | Post Office Protocol version 3 — retrieve email from server | |
| 111 | RPC | TCP/UDP | Other | Remote Procedure Call — SunRPC portmapper |
| 113 | Ident | TCP | Security | Identification protocol — identifies user of a TCP connection |
| 115 | SFTP | TCP | File Transfer | Simple File Transfer Protocol (not SSH-based SFTP) |
| 118 | SQL Services | TCP/UDP | Database | SQL Services |
| 119 | NNTP | TCP | Messaging | Network News Transfer Protocol — Usenet newsgroups |
| 123 | NTP | UDP | Other | Network Time Protocol — clock synchronization |
| 135 | MS-RPC | TCP/UDP | Remote Access | Microsoft Remote Procedure Call (DCE/RPC endpoint mapper) |
| 137 | NetBIOS-NS | UDP | Other | NetBIOS Name Service — Windows network naming |
| 138 | NetBIOS-DGM | UDP | Other | NetBIOS Datagram Service |
| 139 | NetBIOS-SSN | TCP | File Transfer | NetBIOS Session Service — Windows file/print sharing |
| 143 | IMAP | TCP | Internet Message Access Protocol — access email on server | |
| 156 | SQL Service | TCP/UDP | Database | SQL Service |
| 161 | SNMP | UDP | Other | Simple Network Management Protocol — monitoring agents |
| 162 | SNMP Trap | UDP | Other | SNMP Trap — asynchronous notifications from agents |
| 170 | Print Server | TCP | Other | Network PostScript print server |
| 179 | BGP | TCP | Other | Border Gateway Protocol — internet backbone routing |
| 194 | IRC | TCP | Messaging | Internet Relay Chat — real-time text messaging |
| 199 | SMUX | TCP | Other | SNMP Unix Multiplexer |
| 201 | AT-RTMP | TCP | Other | AppleTalk Routing Maintenance |
| 209 | QMTP | TCP | Quick Mail Transfer Protocol | |
| 210 | Z39.50 | TCP | Other | ANSI Z39.50 — library catalog search protocol |
| 213 | IPX | UDP | Other | Internetwork Packet Exchange |
| 220 | IMAP3 | TCP | IMAP version 3 (deprecated) | |
| 259 | ESRO | TCP/UDP | Other | Efficient Short Remote Operations |
| 264 | BGMP | TCP | Other | Border Gateway Multicast Protocol |
| 311 | macOS Server | TCP | Remote Access | macOS Server Admin |
| 318 | TSP | TCP/UDP | Other | PKIX Time Stamp Protocol |
| 323 | IMMP | TCP/UDP | Messaging | Internet Message Mapping Protocol |
| 350 | MATIP-A | TCP | Other | Mapping of Airline Traffic over IP |
| 363 | RSVP | TCP/UDP | Other | RSVP Tunnel |
| 369 | Rpc2portmap | TCP/UDP | Other | Coda filesystem portmapper |
| 371 | Clearcase | TCP/UDP | Other | Clearcase albd |
| 383 | HP Alarm | TCP/UDP | Other | HP data alarm manager |
| 384 | ARNS | TCP/UDP | Other | A Remote Network Server System |
| 387 | AURP | TCP/UDP | Other | AppleTalk Update-Based Routing Protocol |
| 389 | LDAP | TCP/UDP | DNS & Directory | Lightweight Directory Access Protocol — directory services |
| 401 | UPS | TCP/UDP | Other | Uninterruptible Power Supply monitoring |
| 411 | Direct Connect | TCP | File Transfer | Direct Connect Hub |
| 427 | SLP | TCP/UDP | DNS & Directory | Service Location Protocol |
| 443 | HTTPS | TCP | Web | HTTP over TLS/SSL — encrypted web traffic |
| 445 | SMB | TCP | File Transfer | Server Message Block — Windows file and printer sharing |
| 464 | Kpasswd | TCP/UDP | Security | Kerberos password change protocol |
| 465 | SMTPS | TCP | SMTP over SSL (implicit TLS) — secure email sending | |
| 497 | Retrospect | TCP/UDP | Other | Retrospect backup and restore |
| 500 | IKE | UDP | Security | Internet Key Exchange — IPsec VPN key negotiation |
| 502 | Modbus | TCP | Other | Modbus protocol — industrial SCADA communication |
| 512 | Rexec | TCP | Remote Access | Remote process execution |
| 513 | Rlogin | TCP | Remote Access | Remote login (legacy Unix) |
| 514 | Syslog | UDP | Other | System logging protocol — centralized log collection |
| 515 | LPD | TCP | Other | Line Printer Daemon — Unix printing |
| 520 | RIP | UDP | Other | Routing Information Protocol |
| 521 | RIPng | UDP | Other | Routing Information Protocol next generation (IPv6) |
| 530 | RPC | TCP/UDP | Other | Remote Procedure Call |
| 540 | UUCP | TCP | Other | Unix-to-Unix Copy Protocol |
| 543 | KLogin | TCP | Security | Kerberos login |
| 544 | KShell | TCP | Security | Kerberos remote shell |
| 546 | DHCPv6 Client | UDP | Other | DHCPv6 client |
| 547 | DHCPv6 Server | UDP | Other | DHCPv6 server |
| 548 | AFP | TCP | File Transfer | Apple Filing Protocol — macOS file sharing |
| 554 | RTSP | TCP | Web | Real Time Streaming Protocol — media streaming control |
| 556 | RFS | TCP | File Transfer | Remotefs — RFS server |
| 563 | NNTPS | TCP | Messaging | NNTP over TLS/SSL |
| 587 | Submission | TCP | Email message submission (SMTP with STARTTLS) | |
| 591 | FileMaker | TCP | Database | FileMaker Pro web sharing |
| 593 | MS-RPC HTTP | TCP | Remote Access | Microsoft RPC over HTTP |
| 596 | SMSD | TCP | Other | SMSD message relay |
| 631 | IPP | TCP/UDP | Other | Internet Printing Protocol / CUPS printing |
| 636 | LDAPS | TCP | DNS & Directory | LDAP over SSL — secure directory services |
| 639 | MSDP | TCP | Other | Multicast Source Discovery Protocol |
| 646 | LDP | TCP/UDP | Other | Label Distribution Protocol (MPLS) |
| 691 | MS Exchange | TCP | Microsoft Exchange Routing | |
| 860 | iSCSI | TCP | Other | Internet Small Computer System Interface |
| 873 | Rsync | TCP | File Transfer | Rsync file synchronization protocol |
| 902 | VMware | TCP | Remote Access | VMware ESXi management |
| 953 | RNDC | TCP | DNS & Directory | BIND DNS remote name daemon control |
| 989 | FTPS Data | TCP | File Transfer | FTP over TLS/SSL — data channel |
| 990 | FTPS Control | TCP | File Transfer | FTP over TLS/SSL — control channel |
| 992 | Telnets | TCP | Remote Access | Telnet over TLS/SSL |
| 993 | IMAPS | TCP | IMAP over SSL — secure email access | |
| 995 | POP3S | TCP | POP3 over SSL — secure email retrieval | |
| 1023 | Reserved | TCP/UDP | Other | Last well-known port — end of privileged port range |
Port Number Ranges
0 \u2013 1,023 Well-Known Ports Reserved for system services and standard protocols. Require root/admin privileges on most OSes.
1,024 \u2013 49,151 Registered Ports Assigned by IANA for specific services (e.g., 3306 MySQL, 5432 PostgreSQL, 8080 HTTP Alt).
49,152 \u2013 65,535 Dynamic / Ephemeral Used for temporary client-side connections. Not assigned to any service.
Frequently Asked Questions
What does it mean if a port is open vs closed?
Open: a service is actively listening on that port and the firewall allows connections — the tool gets a response. Closed: the host is reachable but nothing is listening on that port (or the firewall actively rejects connections). Filtered/timed out: the host may be unreachable or a firewall is dropping packets without responding.
What are the most important ports to know?
Common ports: 21 (FTP), 22 (SSH), 25 (SMTP email), 53 (DNS), 80 (HTTP), 110 (POP3), 143 (IMAP), 443 (HTTPS), 465/587 (SMTP with SSL/TLS), 3306 (MySQL), 3389 (RDP/Windows Remote Desktop), 5432 (PostgreSQL), 6379 (Redis), 8080/8443 (HTTP/HTTPS alt), 27017 (MongoDB).
Why would a port be open on my server unexpectedly?
An open port you don't recognise could indicate: a service installed by software running on a non-default port, a misconfigured firewall, or potentially unwanted software. Investigate with netstat (Windows/Linux) or lsof -i (macOS/Linux) to identify which process is listening on the port.