diff --git a/pytorch_lightning/models/trainer.py b/pytorch_lightning/models/trainer.py
index f04b1fda61..01f105151a 100644
--- a/pytorch_lightning/models/trainer.py
+++ b/pytorch_lightning/models/trainer.py
@@ -150,7 +150,7 @@ class Trainer(TrainerIO):
         self.node_rank = 0
         self.use_ddp = False
         self.use_dp = False
-        self.default_ddp_port = 12910
+        self._ddp_port = None
 
         # training bookeeping
         self.total_batch_nb = 0
@@ -399,11 +399,29 @@ class Trainer(TrainerIO):
     # MODEL TRAINING
     # -----------------------------
     def __kill_ddp_ports(self, port_nb):
+        def get_pids(port):
+            command = "sudo lsof -i :%s | awk '{print $2}'" % port
+            pids = subprocess.check_output(command, shell=True)
+            pids = pids.strip()
+            if pids:
+                pids = re.sub(' +', ' ', pids)
+                for pid in pids.split('\n'):
+                    try:
+                        yield int(pid)
+                    except:
+                        pass
+
+        # kill all processes on this port
+        pids = set(get_pids(port_nb))
+        command = 'sudo kill -9 {}'.format(' '.join([str(pid) for pid in pids]))
+        os.system(command)
+
+
     def fit(self, model):
 
         # when using multi-node or DDP within a node start each module in a separate process
         if self.use_ddp:
-            self.__kill_ddp_ports(self.default_ddp_port)
+            self.__kill_ddp_ports(self.ddp_port)
 
             # must copy only the meta of the exp so it survives pickle/unpickle when going to new process
             self.experiment = self.experiment.get_meta_copy()
@@ -542,6 +560,19 @@ class Trainer(TrainerIO):
         # continue training routine
         self.__run_pretrain_routine(model)
 
+    @property
+    def ddp_port(self):
+        if self._ddp_port is None:
+            try:
+                port = os.environ['MASTER_PORT']
+            except Exception as e:
+                port = self.default_ddp_port
+                os.environ['MASTER_PORT'] = f'{port}'
+
+            self._ddp_port = port
+
+        return self._ddp_port
+
     def __init_tcp_connection(self):
         """
         Connect all procs in the world using the env:// init
@@ -550,17 +581,11 @@ class Trainer(TrainerIO):
         :param tries:
         :return:
         """
-        try:
-            port = os.environ['MASTER_PORT']
-        except Exception as e:
-            port = self.default_ddp_port
-            os.environ['MASTER_PORT'] = f'{port}'
+        # sets the appropriate port
+        _ = self.ddp_port
 
         root_node = self.__resolve_root_node_address()
         os.environ['MASTER_ADDR'] = root_node
-
-        self.default_ddp_port = port
-
         dist.init_process_group("nccl", rank=self.proc_rank, world_size=self.world_size)