Port number
A port number is a numeric transport-layer identifier that directs network traffic to a service or application endpoint on a host.
Acing the CCNA Exam: Volume 1 Fundamentals and Protocols
A port number is a transport-layer identifier ranging from 0 to 65535 that directs network data to a particular application process on a host.
- How it is used
- Uses transport-layer addressing to deliver messages to application processes and to filter traffic in extended ACLs.
- How deep it goes
- Explains the numeric range, encapsulation, request-reply reversal, common assignments, and extended-ACL matching.
- Examples
- Uses HTTPS on TCP 443, a client source port 50000, common protocol assignments, and Cisco extended-ACL entries.
- What you can do after
- Apply port matching in Cisco extended ACLs and interpret source and destination ports in client-server exchanges.
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Kubernetes in Action, Second Edition
A container port is a network port on which an application in a container accepts connections.
- How it is used
- Identifies where a container application accepts connections and helps configure requests or Service forwarding.
- How deep it goes
- Distinguishes an informative pod port declaration from actual connectivity, then explains Service port and targetPort configuration.
- Examples
- Uses a pod manifest declaring `containerPort: 8080`, requests to a pod IP, and a Service manifest with `port` and `targetPort`.
- What you can do after
- Operate/configure it by recording a container port, finding a pod IP, and choosing a Service targetPort or local port-forward.
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Acing the CCNA Exam: Volume 2 Advanced Networking and Security
A port number is a transport-layer identifier that distinguishes application endpoints and concurrent communication sessions on a host.
- How it is used
- Uses TCP/UDP port numbers to distinguish simultaneous sessions when dynamic PAT maps many inside hosts to shared public addresses.
- How deep it goes
- Explains port allocation, preservation, collisions, persistence, capacity, and ICMP’s Identifier alternative, then demonstrates Cisco configuration and output.
- Examples
- Uses shared-address translation tables, NAT pools, PAT overload commands, and ICMP Identifier handling as concrete examples.
- What you can do after
- Diagnose PAT translations by relating inside-local and inside-global addresses to translated TCP/UDP ports and session entries.
Read how Acing the CCNA Exam: Volume 2 Advanced Networking and Security explains port number →
Learn Go with Pocket-Sized Projects
A network port is a numbered endpoint that identifies a service or connection on a host.
- How it is used
- Uses port numbers to expose Go HTTP and gRPC services for local development and network requests.
- How deep it goes
- Explains virtual endpoints, standard assignments, conflicts, development choices, and Go listener calls without covering deployment or containerization.
- Examples
- Demonstrates HTTP on localhost:8080, curl testing, gRPC on a chosen TCP port, and random allocation through port 0.
- What you can do after
- Operate/configure a Go HTTP or gRPC service by binding it to a chosen port and handling requests.
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.NET in Action, Second Edition
A network port is a numbered endpoint used by networked software to identify a service on a host or container.
- How it is used
- Configures access to a web service running inside a Docker container.
- How deep it goes
- Distinguishes port exposure from publication and demonstrates host-to-container mapping, but does not detail networking internals.
- Examples
- Uses an AsciiArtSvc Dockerfile exposing 5101 and a runtime mapping from host port 5000.
- What you can do after
- Operate/configure a Docker container so a host port reaches the service’s internal listening port.
Read how .NET in Action, Second Edition explains port number →
Amazon Web Services in Action, Third Edition: An in-depth guide to AWS
A network port is a numbered logical endpoint that identifies a service or application protocol on a networked host.
- How it is used
- Controls which network services can reach or leave EC2 instances and related AWS resources.
- How deep it goes
- Explains port-based firewall rules through web, SSH, and EFS examples, but does not develop port internals or application security.
- Examples
- Uses ports 80, 443, 22, and 2049 in web-server, SSH, and EFS mount-target scenarios.
- What you can do after
- Operate/configure security-group rules that expose required services while restricting unnecessary inbound and outbound traffic.
Road to Kubernetes
A port is a numbered network endpoint through which a host or container accepts or sends traffic for an application or service.
- How it is used
- Configures local web access and connects host traffic to applications running inside containers.
- How deep it goes
- Explains defaults, environment and command-line overrides, and host-to-container mappings without descending into networking internals.
- Examples
- Uses Express.js on ports 3000 and 3011, FastAPI on 8011, and Docker mappings from 8080 to NGINX port 80.
- What you can do after
- Operate local applications and containers by selecting reachable ports and applying host-to-container mappings.
Related concepts
- routed portincludes · A routed port is a switch port configured as a Layer 3 router interface rather than a Layer 2 switchport.
- dynamic port address translationused by · Dynamic Port Address Translation is a Network Address Translation technique that dynamically maps many internal hosts to one public IP address by distinguishing connections with transport-layer ports.
- HTTPSused by · HTTPS is HTTP carried over TLS, which provides encryption and endpoint authentication for network communication.
- firewallconfigured by · A firewall is a network security system that monitors and filters communications according to rules governing which traffic is permitted or blocked.
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