New answer, powershell

TCP

Get-Process -Id (Get-NetTCPConnection -LocalPort YourPortNumberHere).OwningProcess

UDP

Get-Process -Id (Get-NetUDPEndpoint -LocalPort YourPortNumberHere).OwningProcess

Old answer, cmd

 C:\> netstat -a -b

(Add -n to stop it trying to resolve hostnames, which will make it a lot faster.)

Note Dane's recommendation for TCPView. It looks very useful!

-a Displays all connections and listening ports.

-b Displays the executable involved in creating each connection or listening port. In some cases well-known executables host multiple independent components, and in these cases the sequence of components involved in creating the connection or listening port is displayed. In this case the executable name is in [] at the bottom, on top is the component it called, and so forth until TCP/IP was reached. Note that this option can be time-consuming and will fail unless you have sufficient permissions.

-n Displays addresses and port numbers in numerical form.

-o Displays the owning process ID associated with each connection.

This is originally from Sara's blog.

It also works with almost any version of Visual Studio, you just need to change the "8.0" in the registry key to the appropriate version number for your version of Visual Studio.

The guide line shows up in the Output window too. (Visual Studio 2010 corrects this, and the line only shows up in the code editor window.)

You can also have the guide in multiple columns by listing more than one number after the color specifier:

RGB(230,230,230), 4, 80

Puts a white line at column 4 and column 80. This should be the value of a string value Guides in "Text Editor" key (see bellow).

Be sure to pick a line color that will be visisble on your background. This color won't show up on the default background color in VS. This is the value for a light grey: RGB(221, 221, 221).

Here are the registry keys that I know of:

Visual Studio 2010: HKCU\Software\Microsoft\VisualStudio\10.0\Text Editor

Visual Studio 2008: HKCU\Software\Microsoft\VisualStudio\9.0\Text Editor

Visual Studio 2005: HKCU\Software\Microsoft\VisualStudio\8.0\Text Editor

Visual Studio 2003: HKCU\Software\Microsoft\VisualStudio\7.1\Text Editor

For those running Visual Studio 2010, you may want to install the following extensions rather than changing the registry yourself:

• http://visualstudiogallery.msdn.microsoft.com/en-us/0fbf2878-e678-4577-9fdb-9030389b338c

• http://visualstudiogallery.msdn.microsoft.com/en-us/7f2a6727-2993-4c1d-8f58-ae24df14ea91

These are also part of the Productivity Power Tools, which includes many other very useful extensions.