Know How...

Sep 11th 2017

Know How... 343

Ports, Pumps and Patrick!

Padre and Patrick answer your questions!

Although the show is no longer in production, you can enjoy episodes from the TWiT Archives.
Category: Help & How To

Open Ports

"I have open ports on my PC to Microsoft. Should I close them?" -- Patrick Sheekey  

  • 135/tcp Microsoft Windows RPC
  • 139/tcp Microsoft Windows NetBIOS-ssn
  • 445/tcp Microsoft-ds Windows 10 Home

These are all Microsoft-service ports

  • 135 (TCP/UDP) - Microsoft Remote Procedure Call - Used in client/server apps (like Exchange, VPN, etc.)
  • 136 (TCP/UDP) - NetBIOS Session Service (A protocol for file and print sharing)
  • 445 (TCP/UDP) - SMB (Server Message Block) -- Protocol for file sharing


  • We're going to run NMAP against the client, then against the router.

Network Testing on the Cheap

 "Does anyone have a good suggestion on how to test if a network jack is live and getting DHCP without plugging in a computer? Sometimes I need to verify several jack in different locations but do not want to carry around my laptop. I was wondering if there is a way to use an Arduino with an ethernet shield and maybe a display to show the IP address. Also needing it run off a battery." -- Brian Ward

Fluke Nettool

Water in my trailer

 "I have a 7Amp DC water pump in my food trailer that killed my car battery. Can you show me how to run it off our electric source instead of the battery source? The pump will only be used when we turn on the water which is maybe once or twice a day. The pump is protected from the weather and used to pump fresh water into the sink. Yes, I do have a power source right next to the pump." -- Hector Sotomayor

First... a little math!

  • It's a DC (probably 12V) pump that requires 7 Amps
    • It PROBABLY only needs 7 Amps at startup (But we still plan for the peak draw)
    • (Watts = Volts X Amps) So... 12 volts x 7 amps = 84 Watts
  • We need to plan to SAFELY provide 84 watts to the pump
    • 120W AC-DC Power Supply
  • 12v 10 Amp Power Supply
    • 12volts x 10 amps = 120 Watts
  • This should be more than enough to power your pump ASSUMING that you're not putting too much load on your AC circuit.

But... What if we were able to pump water... by REMOVING the pump?

4 Gallon RO Water Storage Tank

  • This is a "Bladder Tank"
  • It stores liquid in a food-grade bladder within a steel tank
    • The area between the tank and the bladder is pressurized
    • When water is pumped into the bladder, it increases that pressure (can reach 40-50psi)
  • This allows you to fill the tank with water and the pressure within the tank will force it back out, without the need for a pump!
  • Since you need space for the air and the bladder, a 4 Gallon tank holds ~3 gallons of fluid
  • You want "Food Grade"... and you'll want to filter the water so that you don't fill it with debris or eat away at the bladder with excessive clorine
  • You can change the pressure using the air stem valve


  1. No need for a pump
  2. GREATLY reduces sloshing

Help me start my 3D Projects
"On the advice of Padre and Bryan, I purchased a Monoprice Maker Select v2. I've been mostly printing objects I find on Thingiverse, but I want to start creating my own projects like on Know How. I've been using Tinkercad, and while it is really easy to use, that CAN'T be what Padre ACTUALLY uses for his projects. If it is, then it means that I'm lacking some basic knowledge about designing 3D parts.

"What tips and tricks do I need to know about Tinkercad and 3D design to create Know How caliber projects?" -- Patrick Bolough


  1. A Good Digital Caliper
    • Padre's Pick: iGaging ABSOLUTE ORIGIN 0-6" Digital Electronic Caliper
      • BE WARRY... much of the cheap stuff is JUNK.
      • If you get a nice on, it is ALWAYS in its case when it's not being used.
  2. Techniques
    • Learn the Hotkeys
      • "Control-C" = copy
      • "Control-V" = past in place
      • "d" = drop to platform
      • "CTRL + up or down" = raise or lower by a unit
      • "SHIF + Direction keys or raise/lower" = move 10 units
  3. Templates
    • If you create templates for your most-often used parts, you can deploy questions more quickly

TiVo DVR Replacement

"My Tivo is slowly starting to die. Looking at replacing this with something capable of carrying out my DVR needs. The Tivo is my local and Comcast recording go-to-box, it is simple and no learning curve.
HD-HomeRunPrime is the only device found during my search allowing the use of my Comcast descrambler card and DVR, although they charge 35/Year for the program listing service. Oh and the DVRs are sent to your local NAS.

Any recommendations for the hardware replacement(Tivo) carrying out the same duties as the Tivo?" - Rud  Dog

Option 1: Fix hard drive (Spinrite as suggested by Damien Wessling) rather than entire TiVo.
Option 2: Copy the old drive onto a newer, larger drive to not only fix your TiVo, but upgrade to more space!
Option 3: New TiVo?

  • Pro: Bolt records 4 or 6 shows at once & 4K
  • Con: $200-$500 + $550 Lifetime fee

Option 4: Non-TiVo DVR options: Comcast? Their DVR is not great and laggy.

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