{"data":[{"number":1,"slug":"1-tcpmux","name":"TCPMUX","brief":"The TCP Port Service Multiplexer (TCPMUX) is a protocol used on port 1 to allow clients to query a server for a list of active services and connect to specific daemon processes dynamically. It acts as a service directory or initial contact point, facilitating connection establishment to various services hosted on a server.","commonUsage":"Service Multiplexing","protocols":["tcp","udp"],"transport":{"tcp":true,"udp":true,"sctp":false},"official":true,"encrypted":false,"range":"well-known","risk":{"score":4,"level":"caution"},"categories":[{"name":"Security","slug":"security"},{"name":"Network Services","slug":"network-services"},{"name":"System","slug":"system"}],"aliases":[],"views":12881,"updatedAt":"2026-08-13T12:29:56.180Z","url":"https://whatportis.com/ports/1-tcpmux"},{"number":2,"slug":"2-management-utility","name":"Management Utility","brief":"Port 2 is historically designated for management utilities within networked systems. Although rarely used in modern applications, it can be reserved by legacy services or specialized device management interfaces. Proper awareness of this port is important to avoid misuse or accidental exposure in secure environments.","commonUsage":"System Management","protocols":["tcp","udp"],"transport":{"tcp":true,"udp":true,"sctp":false},"official":true,"encrypted":false,"range":"well-known","risk":{"score":4,"level":"caution"},"categories":[{"name":"Network Services","slug":"network-services"},{"name":"System","slug":"system"}],"aliases":[],"views":10822,"updatedAt":"2026-08-13T12:30:11.812Z","url":"https://whatportis.com/ports/2-management-utility"},{"number":3,"slug":"3-compression-process","name":"Compression Process","brief":"Port 3 is an early legacy assigned port utilized for experimental compression protocols, historically used during development phases of protocols that involved data reduction techniques. It currently holds minimal practical usage but remains listed within the Assigned Numbers Authority for compatibility and archival reasons.","commonUsage":"Legacy compression","protocols":["tcp","udp"],"transport":{"tcp":true,"udp":true,"sctp":false},"official":true,"encrypted":false,"range":"well-known","risk":{"score":4,"level":"caution"},"categories":[{"name":"Network Services","slug":"network-services"},{"name":"System","slug":"system"}],"aliases":[],"views":6928,"updatedAt":"2026-08-13T12:31:02.860Z","url":"https://whatportis.com/ports/3-compression-process"},{"number":4,"slug":"4-unassigned-port-4","name":"Unassigned Port 4","brief":"Port 4 is currently unassigned by IANA and does not have a specific service or protocol officially designated for its use. It remains available for dynamic or private application assignments, often utilized temporarily during testing or for ephemeral purposes across TCP and UDP protocols.","commonUsage":"Unassigned/Reserved","protocols":["tcp","udp"],"transport":{"tcp":true,"udp":true,"sctp":false},"official":false,"encrypted":false,"range":"well-known","risk":{"score":1,"level":"safe"},"categories":[{"name":"Network Services","slug":"network-services"},{"name":"System","slug":"system"}],"aliases":[],"views":5866,"updatedAt":"2026-08-13T12:31:20.638Z","url":"https://whatportis.com/ports/4-unassigned-port-4"},{"number":5,"slug":"5-remote-job-entry","name":"Remote Job Entry","brief":"Remote Job Entry (RJE) is an early protocol designed for submitting batch processing jobs from remote locations to mainframe computers. It facilitated offsite users or departments in efficiently sending jobs and retrieving results without direct access to the data center. RJE was primarily used in large enterprise and academic environments before the advent of modern distributed and interactive systems.","commonUsage":"Batch processing","protocols":["tcp","udp"],"transport":{"tcp":true,"udp":true,"sctp":false},"official":true,"encrypted":false,"range":"well-known","risk":{"score":4,"level":"caution"},"categories":[{"name":"Network Services","slug":"network-services"},{"name":"System","slug":"system"}],"aliases":["rje"],"views":9732,"updatedAt":"2026-08-13T12:30:24.098Z","url":"https://whatportis.com/ports/5-remote-job-entry"}],"meta":{"total":534,"count":5,"limit":5,"offset":0,"hasMore":true,"sort":"number"},"links":{"self":"http://localhost:3000/api/v1/ports?protocol=udp&range=well-known&sort=number&limit=5","next":"http://localhost:3000/api/v1/ports?protocol=udp&range=well-known&sort=number&limit=5&offset=5","prev":null}}