Anyone who has ever flown out of the Dallas Fort Worth (DFW) airport knows that it is huge. The airport itself is actually bigger than the island of Manhattan and, after Atlanta and Chicago, it is the busiest airport in the US.
The fact that it is so spread out is an advantage and a disadvantage. The advantage is that there is rarely any line for security as there are so many entrances. The disadvantage is that if the north parking lot is full, or you have to rent a car, count on an extra half hour to get to your gate as you’ll have to drive a ridiculous distance to get to the remote parking lots and/or rental car facility.
Another disadvantage is the enormous size of its parking lot. A few years ago I returned from a trip overseas, and I was unable to find my car. It was at least 100 degrees, very humid, and I was carrying a big bag filled with chocolate, cheese, coffee and other items that you can only get in Europe. I could have sworn my car was at this gate, and went up and down two levels twice. I finally gave up, hailed a taxi and told him to take me home because I was convinced that my car was stolen. The driver smiled, and said, “Let’s drive through the other parking garages at the different gates and then we can see about filing the missing car report”. After 10 minutes we found my car at another gate. Now I have a system. I write down my departure gate number before I leave my car for the gate and it has worked so far.
My lesson learned is to keep track of your gate numbers. The same applies for your software applications; keep track of your port numbers. I received an e-mail from one of our students to ask for my support as he installed the DICOM simulator we provide in our class on his PC at work. The software was working very erratically, sometimes it worked, and sometimes it did not. He would send a test image from a modality to the simulator, the modality reported a successful transmission, but he could not find any evidence that the image was received and stored.
It took me a little while to remember that I had dealt with this issue before, then I asked whether he had any other DICOM applications running on his PC. He said that he had e-film and KPACS installed, which gave me a clue, and I suggested that he change the port number on the simulator. After that everything was OK.
This is a typical behavior that happens when different applications are using the same port number. Sometimes it is not even obvious as this might happen in the background. For example, if one installs KPACS, the so-called KPserver automatically starts up every time you reboot the system, meaning there is an application listening to port 104. If you configure another application to also use that port, conflicts might arise.
I remember in the early years of PACS when a system in south Texas was working erratically and it took them a few days to figure out that a new device was using a duplicate IP address. This would very likely not happen again as IT departments now know to manage their IP addresses and assign unique numbers to each device. Recently, because of security concerns, IT departments began to restrict information exchanges to only certain port numbers. Therefore, now you need to manage your port numbers just as you manage IP addresses. The first step is to catalogue the ones you use. I have found a wide variety of numbers out there in the field. The most common one is port 104, however, as not every OS would allow access to such a low number, people have started using 5104, or even 6000 or other ports. By having at least a map of your port numbers, you can work with IT to make sure that access is controlled and limited to only these ports.
For every new modality, upgrade, and new installation, I strongly recommend using the “official” DICOM port number 11112, which is assigned by the Internet authority (IANA). I would not recommend changing the port for all your existing devices, rather institute a transition to this port with every change and upgrade. That will prevent potential future conflicts, and if nothing else, if another application claims that port, you have at least the standard as a backup.
In conclusion, as I need to do with my gate numbers, imaging professionals have to manage their port numbers, otherwise, they might find their data parked at the wrong port.
Herman Oosterwijk, VP, OTech Media