DH Port Scanner vs. Other Port Scanners: Features Compared

Troubleshooting Common Issues in DH Port Scanner

DH Port Scanner is a useful tool for discovering open ports and assessing network services. This guide walks through common problems you may encounter, why they happen, and step-by-step fixes so you can get reliable scan results.

1. Scanner returns no hosts or ports

• Possible causes:
  • Target hosts are offline or unreachable.
  • Network firewall or router is blocking scanning traffic.
  • Incorrect target IPs, CIDR, or hostname syntax.
• Fixes:
  1. Verify reachability: Ping or traceroute the target from the scanner host.
  2. Check syntax: Ensure IPs, ranges, or CIDR are correctly formatted (e.g., 192.0.2.0/24).
  3. Test port-level access: Use telnet/nc to attempt connecting to a known open port.
  4. Inspect network controls: Temporarily disable local firewall or run scan from a different network to rule out blocking.

2. Scan results are incomplete or inconsistent

• Possible causes:
  • Network packet loss, rate limiting, or intermittent connectivity.
  • Host-based intrusion prevention or rate-limiting on the target.
  • Scanner timeouts too short for high-latency networks.
• Fixes:
  1. Increase timeouts and retries in DH Port Scanner settings.
  2. Lower scan speed / throttle to avoid triggering rate limits.
  3. Run multiple scans at different times to compare results.
  4. Capture traffic with tcpdump or Wireshark to verify probe/response behavior.

3. False positives (ports shown open but service not reachable)

• Possible causes:
  • Middleboxes or IDS/IPS injecting responses.
  • TCP/IP stack quirks causing SYN-ACKs without service availability.
  • Service bound to localhost only or filtered by host firewall.
• Fixes:
  1. Confirm with direct connection: Use nc/telnet or a browser to connect to the reported port.
  2. Use banner grabbing or application probes to validate service fingerprint.
  3. Scan from a different vantage point to detect middlebox interference.
  4. Check host firewall/service binding (e.g., netstat, ss) to ensure service listens on expected interfaces.

4. Permission or privilege errors

• Possible causes:
  • Raw socket operations require elevated privileges on many systems.
  • Insufficient filesystem permissions for reading/writing reports or configs.
• Fixes:
  1. Run with appropriate privileges (sudo/Administrator) when using raw packet scans.
  2. Adjust filesystem permissions for the scanner user on output directories.
  3. Use non-privileged scan modes if elevation isn’t available (connect scan vs. raw SYN).

5. High CPU, memory usage, or slow performance

• Possible causes:
  • Aggressive parallelism or too many concurrent probes.
  • Large target lists or wide port ranges without batching.
  • Insufficient system resources or I