MoonPoint Support Weblog

Viewing network connections on a Microsoft Windows system by protocol

If you just wish to see TCP ports in use on a Microsoft Windows system, you can issue the netstat -a -p TCP command at a command prompt. The -a parameter specifies all connections and listening ports should be displayed while the -p parameter can be used to select a protocol from TCP, UDP, TCPv6, or UDPv6. If used with the -s option to display per-protocol statistics, the protocol argument may be any of: IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, or UDPv6. If you only wish to view IPv6 TCP ports in use, you can use netstat -a -p TCPv6. If you only wish to see currently established connections, you can pipe the output of the netstat command to the find command. E.g., netstat -a -p TCP | find "ESTABLISHED". Or, if you wished to see all of the TCP ports on which the system was listening for a connection, you could use netstat -a -p TCP | find "LISTENING". If you wanted to see connections to a particular port, e.g., 22, for Secure Shell (SSH) connections, you could use

netstat -a | find ":ssh"

, which would show the IP addresses of the remote systems connected via SSH, or netstat -a | find ":https" for HTTPS connections to web sites. If you wished to see host names rather than IP addresses, you could add the -f option, which displays a Fully Qualified Domain Name (FQDN) instead of an IP address for a remote system. E.g., netstat -a -f | find ":https". Since SSH, HTTP, and HTTPS use TCP rather than UDP transmissions, you don't need to add the -p parameter.

[/os/windows/network] permanent link

Tue, Sep 24, 2024 8:53 pm

Extracting files from a .jar file with the jar command

If you have a JAR ("Java archive") file and wish to extract the files contained within it from a command-line interface (CLI) on a Microsoft Windows system, you can do so by opening a command prompt window and using the jar xf filename.jar command, where filename.jar is the relevant .jar file, if you have the Java Development Kit (JDK) installed on the system — the JDK software can be downloaded for free from Oracle's Java Downloads page.

Minecraft uses .jar files for mods and if you wish to view the models (.json files), textures (.png files) within a JAR file used by Minecraft, you can use the jar xf filename.jar command to see those. If you copy the .jar file to a directory where you wish to extract its contents and then run the command from the directory in which the .jar file is located, you should see a directory named assets appear beneath which you can find blockstates, lang, models, and textures subdirectories. The .json files files, such as those you may see in a models/block subdirectory are JavaScript Object Notation (JSON) files, which you can view or edit in a text editor, such as the Windows Notepad application. The .png files, which you may see in a textures subdirectory are Portable Network Graphics (PNG) files, which you can view or edit in graphics applications such as Microsoft Paint on Microsoft Windows systems. You can also use a tool such as Blockbench to work with the JSON model files and PNG images.

[/os/windows/software/games/minecraft] permanent link

Mon, Sep 23, 2024 7:54 pm

Changing the name of a Cisco switch

To change the name of a Cisco network switch, you can use the command hostname newHostname where newHostname is the new name you wish to apply to the switch. To make the change permanent so the new name is still in place after a reboot, you can follow the command with the write memory command.

Switch>
Switch>enable
Password:
Switch#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)#hostname Styx
Styx(config)#end
Styx#
*Sep 23 01:14:23.917: %SYS-5-CONFIG_I: Configured from console by console
Styx#write memory
Building configuration...
[OK]
Styx#

[/hardware/network/switch/cisco] permanent link

Sun, Sep 22, 2024 9:50 pm

Changing the default gateway address on a Cisco switch

For a Cisco network switch, to change the default gateway address, i.e., to specify the IP address of a router that the switch will use, enter privileged EXEC mode with the enable command, then enter configuration mode with the command configure terminal and then set the default gateway address with the command ip default-gateway gatewayIPAddress where gatewayIPAddress is the address for the router you wish the switch to use. Then exit configuration mode with the end command. To make the change permanent, so that it will persist after a reboot of the switch, enter the command write memory.

Switch>enable
Password:
Switch#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)#ip default-gateway 192.168.1.1
Switch(config)#end
Sep 23 01:26:53.415: %SYS-5-CONFIG_I: Configured from console by console
Switch#write memory
Building configuration...
[OK]
Switch#

You can view the default gateway address with the command show ip default-gateway.

Switch>show ip default-gateway
192.168.1.1
Switch>

[/hardware/network/switch/cisco] permanent link

Mon, Sep 09, 2024 3:07 pm

SolarWinds TFTP Server for Microsoft Windows Systems

If you need a system running a Microsoft Windows operating system to function as a Trivial File Transfer Protocol (TFTP) server, one free solution is the SolarWinds TFTP server program available from the company's website at TFTP Server. After installation of the software, if you open the application, you will see that the TFTP service is started and listening for data on User Datagram Protocol (UDP) port 69.

SolarWinds TFTP Server

If you open a command prompt window and issue the command netstat -anp udp and pipe the output into the find, you should also see the system is listening on all network interfaces, i.e., 0.0.0.0, on UDP port 69.

C:\Users\Public\Downloads>netstat -anp udp | find "0.0.0.0:69"
  UDP    0.0.0.0:69             *:*

C:\Users\Public\Downloads>

The installation program also installs a TFTP service, which is set to run automatically when Windows boots; you can see information on the service if you open Services and scroll through the list of services on the system — you can open a Services window by typing services.msc at a command prompt window and hitting Enter.

[ More Info ]

[/network/tftp] permanent link

Sun, Sep 08, 2024 8:34 pm

Deleting all lines that don't begin with specific text in vim

In the vim text editor, if I want to remove every line in a file that does not contain the word "FALL" in capital letters, I can use :v/FALL/d, i.e., type the colon key and then v, which works like the grep command grep -v to select only lines in a file that don't contain a specified text string. The particular text on which you wish vim to searh is preceded and followed by the slash delimiter with a d at the end to specify you wish those lines not containing the text, e.g., FALL in this case, to be deleted. If I want to delete only those lines that begin with FALL, I can use :v/^FALL/d as the caret specifies that the text should occur at the beginning of lines (a dollar sign, $, would indicate I wanted to select only lines where the text was found at the end of the line). Note: you can also use :g!/^FALL/d to achieve the same end — without the exclamation mark after the global command, all lines containing FALL would be deleted, but as the exclamation mark represents "not", all lines not containing FALL at the beginning of the line are deleted.

[/editors/vi] permanent link

Sat, Sep 07, 2024 9:58 pm

Locating DHCP servers on a LAN from a Microsoft Windows system

If you need to determine the IP addresses of systems on a local area network (LAN) that are functioning as Dynamic Host Configuration Protocol (DHCP) servers, one tool that you can use on systems running a Microsoft Windows operating system is dhcptest, developed by Vladimir Panteleev, aka CyberShadow, a Moldovan developer. He provides a compiled version of the program for Windows systems at dhcptest — there are 32-bit and 64-bit versions of the program there.

When you open the program, type d to have the program send a DHCP discover packet, which should result in responses from DHCP servers on the LAN. You can type Ctrl-C or q to quit the program.