TCP Port Scan

A simple TCP Port Scan to quickly determine the status of an Internet facing service or firewall. Uses the powerful Nmap port scanner. Note that this scan will test for common services only (21) FTP, (22) SSH, (25) SMTP, (80) HTTP, (443) HTTPS and (3389) RDP. Nmap version detection ( -sV ) is enabled.

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Common TCP Ports

21 FTP File Transfer Protocol is a very common service from the early days of the Internet. Allowing transfer of files. A key point on today's modern Internet is that FTP is not an encrypted protocol.
22 SSH Secure SHell is a protocol from remote access to systems usually in a "Terminal Shell". It is an encrypted protocol that performs a similar function to the clear text telnet.
25 SMTP Simple Mail Transport Protocol allows email to be sent from one system to another.
80 HTTP Hyper Text Transport Protocol is the service that delivers web pages to a browser.
443 HTTPS The Secure version of HTTP, this performs the same service of web page delivery but is encrypted using SSL or TLS.
3389 RDP Remote Desktop Protocol is a way to remotely access Windows based systems, giving the user a full desktop environment of the remote computer.

What is this TCP Port Scan?

The TCP Port Scan will test an IP Address for common open ports. This technique of testing for listening services is known as a port scan. Try our advanced online port scanner that is able to scan any IP Address or IP range and all 655535 ports.

Test Firewall through Port Status

By reviewing the results of a TCP Port Scan it is usually possible to determine whether a Firewall is present and blocking all traffic to ports that are not available. If some ports are in a closed state and some filtered this indicates a firewall or router may be blocking traffic but is not necessarily configured correctly as closed ports in most cases should be filtered by the firewall.

In the following example, the ports that are listed as closed responded to the scan with a TCP RST indicating there is no service listening on that port. The filtered services did not respond and the open port responded with a full three way handshake. Check out the Nmap Tutorial for a more in depth explanation.

Nmap scan report for falcon (172.16.2.100)
Host is up (0.00042s latency).
PORT    STATE  SERVICE
21/tcp  filtered ftp
22/tcp  closed ssh
23/tcp  filtered telnet
80/tcp  open   http
443/tcp closed https

Nmap done: 1 IP address (1 host up) scanned in 0.19 seconds

More Nmap Resources

Additional resources are available on:

API for the TCP Port Scan (BETA)

In addition to the web form on this page there is another way to quickly check the port status of the four ports. With this simple API, curl or any other HTTP based tool or software can be used to get the status of ports and often the presence of a firewall. Output is of content type text.

http://api.hackertarget.com/nmap/?q=127.x.x.1

The API is designed to be used in an ad-hoc fashion not for bulk queries and is like all our IP Tools is limited to 50 (total) requests from a single IP Address per day.

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