It was a fine performance from McCullagh and he can build on that victory in 2018.
McCullagh started the first round at a good pace and landed some heavy shots on his German rival but Tran was not here to lie down as they were both defending their unbeaten records.The second road was a rough affair as both fighters resorted to roughing up the other.
The third round was more of the same but McCullagh was doing the better work.
Tran was proving to be tough and awkward in the fourth but McCullagh was getting to him and the German went down for an eight count after a heavy body shot - but he was saved by the bell.
But Tran was stopped in the fifth after taking punishment from McCullagh.
In the main support to the headline act Paddy Gallagher took on Miguel Aguilar.
Gallagher started brightly and put his rival under early pressure in the first round and second round it was more of the same.
In the third both fighters had a go but Gallagher was doing the better work.
Round four was more of the same with both fighters having a go - but Gallagher was always on top.
Aguilar was starting to tire in the fifth as Gallagher applied more pressure.
Gallagher piled on the heat in the sixth and final round but Aguilar held on.
Gallagher winning 60-54 on points.
The Belfast fighter was delighted to finish the year on a high.
"It was a good fight and a good six rounds. I have had a good 2017 and I want to go further next year. I believe I can get better."
Conrad Cummings was in action against Norbert Szekeres.
Cummings will have been looking to get back on track after splitting from trainer Shane McGuigan and manager Barry McGuigan in recent months.
Cimmings started well and looked more relaxed than in previous fights as he worked the head and body.
Cummings piled on the pressure in the second and hurt his opponent with some vicious body shots.
The third was more of the same and Szekeres was tiring as Cummings work took it's toll.
Cummings piled on the pressure but Szekeres was tough nut to crack.
It went to the sixth round and Cummings won clearly 60-54 on points.
And Cummings was pleased to get another win under is belt.
"It was good to get the six rounds and I wanted a stoppage but I thought I boxed well and it was good to get the win.
"I haven't fought in 10 months and I have loads of changes in the background.
"2018 is going to be a big year for me and I am looking forward to moving on with my career."
Belfast's Padraig McCrory was in against Michael Mora.
McCrory boxed well in the first two rounds and was getting down to business as he let his shots go.
And those paid off as he caught Mora with a good shot to the top of the head and the fight was over.
And McCrory was pleased with the win.
"He is an experienced guy with over 30 fights and I knew I hurt him in the second round.
"It was a good win and I am aiming for a huge 2018."
Alfredo Meli was involved in a great scrap with Jade Karam.
Meli has ability and just needs to be more active if he wants to do anything in the sport.
It was a good performance from Meli and he won 60-54 on points.
Meli said: "It was my first fight in nine months and it was good to get six rounds. I want to be more active and I want to be out again early in 2018. I want to be busy and I want a shot at any title."
There was also a win for Taylor McGoldrick on his debut and Steve Collins jnr.