Fundamental network tools

Most of a non-functional tester’s work is based on working with the network. To be able to work more efficiently, we have prepared an overview of the most commonly used tools and explained how to use them in a basic way.

ping

Ping is one of the basic Internet programs that allows you to check whether the target IP address or a domain exists and accepts network requests. Another reason to use “ping” is to check whether the host computer you want to communicate with is working. An example command to check the connection to the target address could look like the following:

$ ping google.com

If you get a response like in the example below, it means that it is possible to reach the host computer.

$ ping google.com
Pinging google.com [142.250.75.14] with 32 bytes of data:
Reply from 142.250.75.14: bytes=32 time=28ms TTL=58
Reply from 142.250.75.14: bytes=32 time=84ms TTL=58
Reply from 142.250.75.14: bytes=32 time=10ms TTL=58

telnet

The telnet command uses the TCP protocol for a remote session (replaced by ssh due to telnet’s lack of encryption). Telnet, because of its simplicity, is often used to check if a connection to a particular port is possible.

Example usage:

$ telnet google.com 443

When the port is closed, we get a notification like at the bottom.

$ telnet google.com 44332
Connecting To google.com...Could not open connection to the host, on port 44332: Connect failed

traceroute / tracert / tracepath

Traceroute (also known as tracert or tracepath) is used to retrieve information about the path through which a transmitted packet passes. We get this information by asking each router along the way for a response. This is how we get the path a packet travels on its way to its destination. Ultimately, traceroute is supposed to help us understand where network problems occur.

$ tracert google.com

Tracing route to google.com [142.250.75.14]
over a maximum of 30 hops:
 1     1 ms     5 ms     2 ms  netiaspot.home [192.168.1.254]
 2    10 ms    10 ms    12 ms  83.238.252.80
 3     5 ms     8 ms     9 ms  wrocc002rt09.inetia.pl [83.238.113.28]
 4    12 ms    14 ms    14 ms  POZNH002RT09.inetia.pl [83.238.248.22]
 5    18 ms    16 ms    31 ms  WARSC001RT06.inetia.pl [83.238.248.16]
 6    20 ms    16 ms    13 ms  72.14.203.16
 7    12 ms    10 ms    12 ms  142.250.227.13
 8    11 ms    17 ms    12 ms  142.250.238.1
 9    10 ms    19 ms    19 ms  waw07s03-in-f14.1e100.net [142.250.75.14]

Trace complete.  

ipconfig

To display all configured network interfaces, their ip addresses, dns servers and other information, we use the ipconfig (windows) or ifconfig (Linux) command, depending on the operating system you are using.

Another interesting option ipconfig (on windows) is the ability to release and renew a new ip address. How to do it: First use the command ipconfig /release and then ipconfig /renew.

Then, in the event that we want to force windows to clear the DNS cache, use the command ipconfig /flushdns.

netstat

The netstat command displays incoming and outgoing network connections and network information. To check all connections we will use the netstat -a command.

$ netstat -a

Active Connections

  Proto  Local Address          Foreign Address        State
  TCP    0.0.0.0:135            DESKTOP-9P879SS:0      LISTENING
  TCP    0.0.0.0:445            DESKTOP-9P879SS:0      LISTENING
  TCP    0.0.0.0:1042           DESKTOP-9P879SS:0      LISTENING
  TCP    0.0.0.0:1043           DESKTOP-9P879SS:0      LISTENING
  TCP    0.0.0.0:3306           DESKTOP-9P879SS:0      LISTENING

We can use netstat to display information about the programs that are making connections. We will use the netstat -b command for this.

$ netstat -b

Active Connections

  Proto  Local Address          Foreign Address        State
  TCP    127.0.0.1:1042         kubernetes:49718       ESTABLISHED
 [asus_framework.exe]
  TCP    127.0.0.1:1042         kubernetes:49719       ESTABLISHED
 [asus_framework.exe]
  TCP    127.0.0.1:9012         kubernetes:49725       ESTABLISHED
 [ArmourySocketServer.exe]
  TCP    127.0.0.1:17532        kubernetes:49720       ESTABLISHED
 [ArmouryCrate.Service.exe]
  TCP    127.0.0.1:49671        kubernetes:49672       ESTABLISHED
 [mysqld.exe]
  TCP    127.0.0.1:49672        kubernetes:49671       ESTABLISHED
 [mysqld.exe]

nmap

Nmap is a tool used to scan ports and network services. To check which ports are open (from o 0 to 65535) we will use the nmap -p- 192.168.0.1 command. However, this is a long process. If we want to check the opening of only the most frequently used ports, we will use the nmap -F 192.168.0.1 command. On the other hand, to check a specific port, we will define the p argument: nmap -p 80 192.168.0.1.

Nmap is a powerful tool and gives us the ability to scan after a TCP connection, SYN or even provide scripts to detect network vulnerabilities. However, these are advanced aspects of using nmap, which we will describe in the future.