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Port Check, Ping and Traceroute

Port check shows open, closed and filtered TCP ports, ping measures response time and packet loss, and traceroute shows the route to a host.

Is a server reachable at all, and if not, where does it get stuck? Three tools in the Netzwerk (network) category answer that. All three require a license and only run in the desktop apps (macOS, Windows, Linux). They are hidden in the web version and on iOS and Android.

Port check

The Port-Check tries to open a TCP connection to each given port.

  1. In the Host oder IP field, enter a hostname or address, for example inwendo.de.
  2. Adjust the list in the Ports field. The defaults are common ports for FTP, SSH, SMTP, DNS, HTTP(S), POP3, IMAP, MySQL, RDP and PostgreSQL. You can give single ports and ranges, for example 22, 80, 443, 8000-8010. A range may cover at most 1024 ports.
  3. Click Prüfen (check).

If you enter host:port, the app checks only that one port. It resolves a hostname first and prefers the IPv4 address. Up to 20 ports run in parallel, each with a three-second timeout.

Status Meaning
offen open: a service accepts connections.
geschlossen closed: the host answers, but nothing runs on the port.
gefiltert (keine Antwort) filtered (no answer): a firewall drops the packets, at the target or in your own network.

Findings

  • … von … Ports offen (… of … ports open) or Kein Port offen (no port open) sums up the result.
  • Port … aus dem Internet erreichbar (reachable from the internet) warns about open ports of databases (MySQL, PostgreSQL, MS SQL, Redis, MongoDB, Elasticsearch), remote access (RDP, VNC, Telnet), FTP and file sharing (SMB). They don’t belong open on the internet. Restrict them to known addresses with a firewall or only offer them over VPN.
  • Gefiltert heißt: keine Antwort (filtered means no answer) explains that the block may be in your own network. Port 25, for instance, is often blocked by your own ISP, see SMTP test.

Ping

Ping sends four ICMP packets to the host and measures the response times. The app uses the operating system’s ping program for this. Enter a host or IP and click Ping.

The table shows sent, received, loss and minimum, average and maximum response time, followed by each individual reply. The program’s output is under Rohdaten (raw data).

Finding (as shown in the app) Meaning
… erreichbar, im Mittel … ms reachable, average … ms: OK.
… % Paketverlust packet loss: some packets didn’t come back, which points to an overloaded or disrupted connection.
… antwortet nicht auf Ping doesn’t answer ping. Many servers and firewalls drop ICMP on purpose; that doesn’t mean the host is offline. Use the port check to see whether a service answers.

Traceroute

Traceroute shows the hops (routers) on the way to a host. Enter a host or IP and click Verfolgen (trace). The app uses the system program: traceroute on macOS and Linux, falling back to tracepath, and tracert on Windows. Up to 30 hops are traced, and a run may take up to two minutes.

The Route zu … table shows each hop with number, address and time. A * means this hop didn’t answer.

Finding Meaning
Ziel nach … Stationen erreicht target reached after … hops: OK.
Ziel nicht bis zum Ende verfolgt not traced to the end. Routers and firewalls often don’t answer traceroute packets; the target can still be reachable.
… Station(en) ohne Antwort („*“) hops without answer, usually filtered on purpose, not an error.
Kein Traceroute-Programm gefunden no traceroute program found. On Linux, install the traceroute or iputils-tracepath package.

See also