Port Checker

Purpose & User Intent: The port checker verifies reachability of specified ports on a host from the tester’s network. Primary users include IT admins, developers, security engineers, QA teams, and incident responders who need to confirm service exposure, diagnose firewall rules, or validate network paths without installing software. It is used during deployment, integration testing, and connectivity triage across data centers, cloud environments, and edge locations.
Core Logic & Features: The tool accepts host, port(s) or ranges, and protocol (TCP by default; UDP optional). Core features include host input, port specification (single port, comma-separated list, or dash ranges), protocol selection, and timeout control; outputs per port: status (open/closed/timeout/filtered), latency, and an optional reason. Optional features include port-range expansion, concurrent checks, and machine-readable outputs for automation.
Inputs & Outputs: Inputs: host (string, required), ports (string or list, required), protocol (TCP|UDP, default TCP), timeout (seconds, optional), concurrency (integer, optional). Outputs: per port: port, status, latency_ms, and optional reason; an overall summary with counts and a pass/fail indicator. Outputs are designed for integration with monitoring dashboards and incident playbooks.
Algorithms & Calculations: For TCP, the tool attempts a socket connect, recording success or timeout and measuring latency from start to connect. For UDP, a minimal probe is sent and state inferred from response or timeout. Ports are tested in parallel up to a configurable concurrency. Results are returned as a structured object suitable for automation.
Error & Edge Cases: Invalid host, malformed port specs, or impossible timeouts yield explicit errors. DNS failures, rate limits, or network restrictions can block tests. The tool does not perform stealth scanning or vulnerability assessment; uses standard IP and DNS semantics.
Industry/Region & Localization: Uses standard IP and DNS naming; supports international hostnames. Time formatting and language considerations are left to the integration.
Assumptions & Exclusions: Assumes authorization to probe targets. Excludes covert scanning, credentialed checks, banner grabbing, and vulnerability assessment. Intended strictly for reachability testing and basic exposure verification.