TCP and UDP Ports – Free, Online, Private

IANA name versus the process you run

A port number is a 16-bit field in a TCP or UDP header. IANA keeps a registry of service names for those numbers. The registry is not a lock. Any process with permission can bind a number, including a number assigned to a service the process does not implement. The pages here say the IANA service name first, then the program people actually run when that program is not the registered service. Port 3000 is hbci in the registry and a development server in most repositories. Port 6443 is sun-sr-https in the registry and the Kubernetes API in most clusters. Both facts belong on the page.

Numbers 0 through 1023 are the well-known range. Binding them on Unix needs extra privilege, or a capability such as CAP_NET_BIND_SERVICE. Numbers 1024 through 49151 are registered. Numbers 49152 through 65535 are dynamic and are what a client uses as an ephemeral source port. A service that listens in the dynamic range will collide with outgoing connections. Do not pick one.

Listening is not reachable

ss and lsof ask the local host. nc asks a remote host. A socket in LISTEN and a timeout from the outside means a firewall or a security group is dropping the packet. A connection refused means a host sent a reset, which usually means nothing is listening or a policy rejected the handshake. UDP has no handshake, so an empty nc exchange does not prove a DNS server or an NTP server is healthy. The detail pages say which transport to test.

The filter on this page runs in the browser. It matches the number, the IANA service name, the common name, and the protocol. Nothing you type is uploaded. The command blocks are copy-paste text. This site does not open a socket to your host.

The ports

Port 22 is IANA service ssh (TCP). TCP 22 is the IANA ssh port. OpenSSH and every other SSH server use it for remote login and file transfer. Port 25 is IANA service smtp (TCP). TCP 25 is the IANA smtp port for server-to-server mail transfer. User clients should submit on 587 or 465, not here. Port 53 is IANA service domain (TCP and UDP). Port 53 is the IANA domain port. DNS queries use UDP, and they use TCP when the answer is truncated or the query is a transfer. Port 67 is IANA service bootps (UDP). UDP 67 is the IANA bootps port, the DHCP and BOOTP server. Clients use UDP 68. The exchange is broadcast and does not cross a router unless a relay is configured. Port 80 is IANA service http (TCP). TCP 80 is the IANA http port. Browsers use it for cleartext HTTP and for the redirect onto HTTPS. Port 110 is IANA service pop3 (TCP). TCP 110 is the IANA pop3 port, cleartext Post Office Protocol. POP3 over TLS is 995. Port 123 is IANA service ntp (UDP). UDP 123 is the IANA ntp port. Clients and servers both use it, and a TCP probe will not tell you if time sync works. Port 143 is IANA service imap (TCP). TCP 143 is the IANA imap port, cleartext IMAP. IMAP over TLS is 993, and UDP 143 is reserved. Port 161 is IANA service snmp (UDP). UDP 161 is the IANA snmp port. Agents answer queries there. Traps are a different port, 162, and a TCP probe does not test SNMP. Port 194 is IANA service irc (TCP). TCP 194 is the IANA irc port. Most networks never used it. They use 6667 and 6697, which are not this assignment. Port 389 is IANA service ldap (TCP). TCP 389 is the IANA ldap port. LDAPS is 636. Cleartext LDAP should not be how you bind over a network you do not trust. Port 443 is IANA service https (TCP). TCP 443 is the IANA https port, HTTP over TLS. Browsers use it by default. UDP 443 is also QUIC. Port 445 is IANA service microsoft-ds (TCP). TCP 445 is the IANA microsoft-ds port. It is SMB, and it should not be reachable from the internet. Port 465 is IANA service submissions (TCP). TCP 465 is IANA submissions, message submission over TLS, from RFC 8314. The registry also still lists urd on 465. Mail clients know it as implicit TLS SMTP. Port 514 is IANA service syslog (UDP). UDP 514 is the IANA syslog port. TCP 514 is a different service, shell. Do not treat a TCP probe of 514 as a syslog test. Port 587 is IANA service submission (TCP). TCP 587 is the IANA submission port. Authenticated users send mail here and upgrade with STARTTLS. Server-to-server mail stays on 25. Port 631 is IANA service ipp (TCP). TCP 631 is the IANA ipp port, the Internet Printing Protocol. CUPS listens here. It is also a small HTTP server and should not be exposed. Port 636 is IANA service ldaps (TCP). TCP 636 is the IANA ldaps port, LDAP over TLS from the first byte. Cleartext LDAP with STARTTLS is 389. Port 853 is IANA service domain-s (TCP and UDP). Port 853 is the IANA domain-s port. DNS over TLS uses TCP. DNS over QUIC uses UDP. Ordinary DNS stays on 53. Port 873 is IANA service rsync (TCP). TCP 873 is the IANA rsync port, used by the rsync daemon. rsync over SSH uses port 22 and never opens 873. Port 993 is IANA service imaps (TCP). TCP 993 is the IANA imaps port, IMAP over TLS from the first byte. Cleartext IMAP with STARTTLS is port 143. UDP 993 is reserved. Port 995 is IANA service pop3s (TCP). TCP 995 is the IANA pop3s port, POP3 over TLS from the first byte. Cleartext POP3 is port 110. Port 1080 is IANA service socks (TCP). TCP 1080 is the IANA socks port. A SOCKS5 proxy accepts a TCP control connection here. UDP associate is negotiated inside that connection. Port 1194 is IANA service openvpn (TCP and UDP). Port 1194 is the IANA openvpn port, on UDP and TCP. The usual deployment is UDP. TCP is a fallback for networks that block UDP. Port 1433 is IANA service ms-sql-s (TCP). TCP 1433 is the IANA ms-sql-s port, the default SQL Server listener. The UDP row in the registry is not how clients connect. Port 1521 is IANA service ncube-lm (TCP). TCP 1521 is the IANA ncube-lm port, nCube License Manager. Oracle Database's listener uses 1521 by long convention, and that use is not the IANA service name. Port 1883 is IANA service mqtt (TCP). TCP 1883 is the IANA mqtt port, cleartext MQTT. MQTT over TLS is 8883, secure-mqtt. Brokers do not speak MQTT on UDP. Port 2049 is IANA service nfs (TCP and UDP). Port 2049 is the IANA nfs port, Sun's Network File System, on TCP, UDP, and SCTP. The registry also records a conflict with shilp on the same number. Port 2181 is IANA service eforward (TCP). TCP 2181 is the IANA eforward port. Apache ZooKeeper's client port is 2181 by convention, and that is not the registered service name. Port 2375 is IANA service docker (TCP). TCP 2375 is the IANA docker port, the Docker Engine API in cleartext. TLS is 2376, docker-s, which is a different assignment. UDP 2375 is reserved. Port 2379 is IANA service etcd-client (TCP). TCP 2379 is the IANA etcd-client port. etcd serves its client API here. Peer traffic is 2380, etcd-server, not this port. UDP 2379 is reserved. Port 3000 is IANA service hbci (TCP). TCP 3000 is the IANA hbci port. A second registry row, remoteware-cl, records an unassigned but widespread use. Development servers use 3000 by convention, which is neither of those names. Port 3306 is IANA service mysql (TCP). TCP 3306 is the IANA mysql port. MySQL and MariaDB listen here by default. The protocol is not encrypted unless you turn TLS on. Port 3389 is IANA service ms-wbt-server (TCP). TCP 3389 is the IANA ms-wbt-server port, Remote Desktop Protocol. UDP 3389 is also used by newer RDP for the graphics stream. Port 3478 is IANA service stun (TCP and UDP). Port 3478 is the IANA stun port, and also turn and stun-behavior. STUN and TURN clients use UDP first. TCP is the fallback. Port 5000 is IANA service commplex-main (TCP). TCP 5000 is the IANA commplex-main port. The registry gives the service name and no description. Flask's default and the macOS AirPlay receiver both use 5000 by convention. Port 5222 is IANA service xmpp-client (TCP). TCP 5222 is the IANA xmpp-client port. Clients connect here. Server-to-server XMPP is 5269, which is not this assignment. UDP 5222 is reserved. Port 5353 is IANA service mdns (UDP). UDP 5353 is the IANA mdns port, multicast DNS, RFC 6762. Queries go to 224.0.0.251, not to a unicast server. TCP 5353 is registered and is not the traffic. Port 5432 is IANA service postgresql (TCP). TCP 5432 is the IANA postgresql port. The server speaks its own protocol, and it can reject a connection in pg_hba.conf after the TCP handshake succeeds. Port 5672 is IANA service amqp (TCP). TCP 5672 is the IANA amqp port. AMQP 0-9-1 brokers, including RabbitMQ, listen here. AMQP 1.0 and TLS use other ports. SCTP is also registered. Port 5900 is IANA service rfb (TCP). TCP 5900 is the IANA rfb port, Remote Framebuffer, the protocol VNC uses. Displays after the first are 5901 and up. UDP is registered and is not the session. Port 6379 is IANA service redis (TCP). TCP 6379 is the IANA redis port. Redis speaks RESP on that socket. UDP 6379 is reserved. A default install often has no authentication. Port 6443 is IANA service sun-sr-https (TCP). TCP 6443 is the IANA sun-sr-https port, Service Registry Default HTTPS. The Kubernetes API server uses 6443 by convention, and that is not the registered service. Port 8000 is IANA service irdmi (TCP). TCP 8000 is the IANA irdmi port, described as iRDMI. Development servers and proxies use it as an unofficial HTTP port. It is not http-alt. That name belongs to 8080. Port 8080 is IANA service http-alt (TCP). TCP 8080 is the IANA http-alt port, HTTP Alternate, with a note to see port 80. Proxies, application servers, and admin UIs listen here. It is not port 591 and not port 8008. Port 8443 is IANA service pcsync-https (TCP). TCP 8443 is the IANA pcsync-https port, PCsync HTTPS. Application servers use it as an unofficial alternate HTTPS port. The registered HTTPS port remains 443. Port 8883 is IANA service secure-mqtt (TCP). TCP 8883 is the IANA secure-mqtt port, MQTT over TLS. Cleartext MQTT is 1883. The first packet on 8883 is a ClientHello, not an MQTT CONNECT. Port 9092 is IANA service XmlIpcRegSvc (TCP). TCP 9092 is the IANA XmlIpcRegSvc port, Xml-Ipc Server Reg. Apache Kafka brokers use 9092 by convention, and that is not the registered service name. Port 9200 is IANA service wap-wsp (TCP). TCP 9200 is the IANA wap-wsp port, the WAP connectionless session service. Elasticsearch's HTTP API uses 9200 by convention. The transport port 9300 is not this assignment. Port 9418 is IANA service git (TCP). TCP 9418 is the IANA git port, the git pack transfer service. The git daemon uses it. git over SSH uses 22, and git over HTTPS uses 443. Port 11211 is IANA service memcache (TCP and UDP). Port 11211 is the IANA memcache port, the memory cache service, on TCP and UDP. Memcached has no authentication in the classic protocol. Port 27017 is IANA service mongodb (TCP). TCP 27017 is the IANA mongodb port, assigned in 2019. The wire protocol is MongoDB's, and it is not encrypted unless you enable TLS. UDP 27017 is reserved.