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About Port Checker

Test if specific TCP ports are open and accessible from multiple global locations. Check common ports like HTTP (80), HTTPS (443), SSH (22), and more.

Check if ports are open and accessible from multiple global locations.

Key Features

  • Multi-region port check
  • Common port presets
  • Single port verification
  • TCP connectivity test
  • Firewall testing

How Port Checker Works

ProbeOps Port Checker tests from 6 global locations to provide comprehensive results. When you run a check, our probe nodes in US East (Virginia), US West (Oregon), EU Central (Helsinki), AP South (Mumbai), CA Central (Canada), AP Southeast (Sydney) simultaneously query the target to identify regional differences and ensure global accessibility.

Results are returned in real-time with detailed breakdowns per region, allowing you to identify location-specific issues that might affect your users in different geographic areas.

Common Use Cases

  • Trace network paths to identify routing issues
  • Verify port accessibility through firewalls
  • Diagnose latency problems hop-by-hop
  • Test service availability from external locations

Related Tools

You might also find these ProbeOps tools useful for your diagnostics:

Specialized Variants

ProbeOps offers specialized versions of Port Checker for specific use cases:

  • Open Port Checker - Check if ports are open from multiple global locations. Verify service accessibility and firewall configuration.
  • Firewall Port Tester - Test if your firewall configuration allows or blocks specific ports from different geographic locations.

API Access

All ProbeOps tools are available via REST API for automation and integration. The Port Checker can be called programmatically from your applications, CI/CD pipelines, or monitoring scripts. See our API documentation for integration guides.

Pricing

Port Checker is available on all ProbeOps plans including our free tier. Free users get 100 probes per month with access to 2 regions. Paid plans starting at $19/month include unlimited regions and higher limits. See pricing details.

Online Port Checker

Check if ports are open and accessible from multiple global locations.

What This Checks
Multi-region port checkCommon port presetsSingle port verificationTCP connectivity testFirewall testing

About Port Checker

Test if specific TCP ports are open and accessible from multiple global locations. Check common ports like HTTP (80), HTTPS (443), SSH (22), and more.

Key Features

Multi-region port check

Common port presets

Single port verification

TCP connectivity test

Firewall testing

Also Available via API & MCP Server

Automate port checker checks in your CI/CD pipelines or run them directly from your AI coding agent.

REST API

Single endpoint, JSON response. Integrate into any language or platform.

cURL

curl -X POST https://probeops.com/api/v1/run \
  -H "X-API-Key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"tool": "port_check", "target": "example.com"}'
Learn more about the API

MCP Server

Works with Claude Code, Cursor, Windsurf, and any MCP-compatible IDE.

Claude Code

> Check the port checker for example.com

Claude uses the probeops_port_check tool to run
the check from 6 global regions and returns
structured results.
Learn more about the MCP Server

Port checking verifies whether specific network ports are open and accepting connections—essential for confirming services are accessible, troubleshooting connectivity issues, and auditing server security. An open port means a service is listening; closed or filtered means it's not accessible.

Our multi-region port checker tests connectivity from 6+ global locations, revealing if ports are accessible worldwide or blocked in specific regions. This helps identify firewall misconfigurations, ISP-level blocking, and geo-restriction issues.

For comprehensive server diagnostics, also run traceroute to verify network path and latency test to measure response times once connectivity is confirmed.

**Methodology:** TCP connect to specified port from 6 regions with 10-second timeout, reporting open/closed/filtered status.

Common Errors & How to Fix Them

Click to expand troubleshooting steps

What This Means

The traceroute couldn't complete—no response received from destination. Packets may be blocked by a firewall, or the destination is unreachable.

How to Fix

1) Verify destination is reachable: ping target.com. 2) Try different protocols: traceroute -I (ICMP) vs traceroute -U (UDP) vs traceroute -T (TCP). 3) Check if destination firewall blocks traceroute. 4) Test from different source location. Some hosts simply block all traceroute traffic.

traceroute timeoutno responsedestination unreachable

What This Means

Traceroute shows hops up to a point, then only asterisks. Traffic is being blocked or dropped at that hop.

How to Fix

1) Identify the last responding hop—that's where blocking occurs. 2) Check if it's your ISP, a transit provider, or destination's network. 3) Try TCP traceroute: traceroute -T -p 443 target.com. 4) Contact the network operator if it's a provider issue. 5) If destination's network, firewall is blocking.

partial traceroutestopsblockedasterisks

What This Means

Traceroute shows the same IP addresses repeating. Packets are going in circles due to misconfigured routing tables.

How to Fix

1) Note the IPs involved in the loop. 2) If it's within your network: check router configurations for circular routes. 3) If it's external: report to ISP with traceroute output. 4) Try alternative route: use VPN to bypass problematic path. Routing loops are usually resolved within hours by network operators.

routing loopcircular routerepeating hops

What This Means

One or more hops show significantly higher latency than others. Could indicate congestion, distance, or router performance issues.

How to Fix

1) Check if high latency persists to destination or recovers. 2) If only that hop is slow: router may deprioritize ICMP (not a real problem). 3) If latency stays high: bottleneck identified. 4) For geographic hops (100ms+ jumps): expected for intercontinental links. 5) Persistent issues: contact ISP with evidence.

high latencyslow hopbottleneckcongestion

What This Means

The port actively refused the connection. Either no service is listening on this port, or it's configured to reject connections.

How to Fix

1) Verify service is running: systemctl status service-name. 2) Check service is on correct port: netstat -tlnp | grep PORT. 3) Ensure service binds to 0.0.0.0, not 127.0.0.1. 4) Check service configuration for listen address/port. 5) Restart service: systemctl restart service-name.

port closedconnection refusedservice not running

What This Means

No response received—a firewall is silently dropping packets to this port. The port may or may not have a service listening.

How to Fix

1) Check local firewall: ufw status, iptables -L -n. 2) For cloud: check security groups (AWS), firewall rules (GCP), NSG (Azure). 3) Check host-level firewall (Windows Firewall). 4) Verify ISP isn't blocking: test from different network. 5) Add firewall rule: ufw allow PORT/tcp.

port filteredfirewallblockedno response

What This Means

The connection attempt timed out. Server may be overloaded, port may be filtered, or there's network congestion.

How to Fix

1) Try with longer timeout: nc -vz -w 10 host port. 2) Check if server is overloaded: verify other services respond. 3) Test from different location to rule out network issues. 4) Check server resources: CPU, memory, connection limits. 5) Review firewall logs for dropped packets.

timeoutconnection timeoutslow response

What This Means

Cannot reach the host at all—not just the specific port. The server may be down, or there's a routing problem.

How to Fix

1) Verify hostname resolves: dig hostname A. 2) Try ping: ping hostname. 3) Check server status in cloud console if applicable. 4) Try traceroute to identify where connectivity breaks. 5) If server is up but unreachable: check network configuration, routing tables.

host unreachableserver downno route

Frequently Asked Questions

Common questions answered

Traceroute shows the path network packets take from source to destination, revealing each router (hop) along the way. It works by sending packets with increasing TTL (Time To Live) values—each router decrements TTL and returns a response when it reaches zero. This maps the complete route and measures latency at each hop.

traceroutebasics

Each line shows a hop number, router IP/hostname, and three response times (in milliseconds). Asterisks (*) mean the router didn't respond—this doesn't always indicate a problem, as some routers are configured not to respond to traceroute. Look for sudden latency increases between hops to identify bottlenecks.

tracerouteinterpretation

Asterisks indicate the router at that hop didn't respond within the timeout period. Common reasons: firewall blocking ICMP/UDP, router configured to deprioritize or ignore traceroute packets, or rate limiting. If subsequent hops respond normally, it's not a problem—some routers simply don't respond to diagnostic traffic.

traceroutetroubleshooting

Network paths vary by geography. A traceroute from the US to a server in Germany takes a different route than from Asia. Multi-region traceroute reveals routing inefficiencies, identifies regional network issues, and helps diagnose "works from here but not there" problems. It's essential for global services.

tracerouteregions

Ping tests if a destination is reachable and measures round-trip time, but only shows the final result. Traceroute shows every hop along the path, helping you identify WHERE problems occur—not just that there IS a problem. Use ping for quick reachability checks; use traceroute to diagnose routing issues.

traceroutecomparison
How to Check if Ports are OpenStep-by-step guide with examples and troubleshooting tips

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Specialized Versions

Open Port CheckerCheck if ports are open from multiple global locations. Verify service accessibility and firewall configuration.
Firewall Port TesterTest if your firewall configuration allows or blocks specific ports from different geographic locations.

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Verify SSL certificates, DNS records, and connectivity from 6+ regions worldwide.

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Last updated: January 27, 2026