TMSS-139: use a preferred port if available, otherwise a random free port

LCS/PyCommon/util.py

@@ -194,12 +194,19 @@ def single_line_with_single_spaces(lines: str) -> str:
             return line
         length = new_length
 
-def find_free_port():
-    '''find and return a random free network port'''
+def find_free_port(preferred_port: int=0):
+    '''find and return a random free network port, preferably the given <preferred_port>'''
     import socket
     from contextlib import closing
 
     with closing(socket.socket(socket.AF_INET, socket.SOCK_STREAM)) as s:
+        try:
+            s.bind(('', preferred_port))
+        except OSError as e:
+            if e.errno==98: # OSError: [Errno 98] Address already in use
                 s.bind(('', 0))
+            else:
+                raise
+
         s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
         return s.getsockname()[1]

SAS/TMSS/test/test_utils.py

@@ -233,7 +233,7 @@ class TMSSTestEnvironment:
         self.database = TMSSTestDatabaseInstance()
         self.django_server = TMSSDjangoServerInstance(db_dbcreds_id=self.database.dbcreds_id,
                                                       ldap_dbcreds_id=self.ldap_server.dbcreds_id,
-                                                      port=find_free_port())
+                                                      port=find_free_port(8000))
 
     def start(self):
         self.ldap_server.start()