diff --git a/spacy/util.py b/spacy/util.py
index f3d5046be..24f12fe65 100644
--- a/spacy/util.py
+++ b/spacy/util.py
@@ -1739,8 +1739,13 @@ def all_equal(iterable):
     return next(g, True) and not next(g, False)
 
 
-def is_port_in_use(port, host="localhost"):
-    """Check if localhost:port is in use."""
+def _is_port_in_use(port: int, host="localhost") -> bool:
+    """Check if 'host:port' is in use. Return True if it is, False otherwise.
+
+    Keyword arguments:
+    port -- the port to check
+    host -- the host to check (default "localhost")
+    """
     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     try:
         s.bind((host, port))
@@ -1751,24 +1756,31 @@ def is_port_in_use(port, host="localhost"):
         s.close()
 
 
-def find_available_port(start, host, auto_select=False):
+def find_available_port(start: int, host: str, auto_select=False) -> int:
     """Given a starting port and a host, handle finding a port.
 
     If `auto_select` is False, a busy port will raise an error.
 
     If `auto_select` is True, the next free higher port will be used.
+
+    Keyword arguments:
+    start -- the port to start looking from
+    host -- the host to find a port on
+    auto_select -- whether to automatically select a new port if the given port is busy (default False)
+
+    RETURNS (int): The port to use.
     """
-    if not is_port_in_use(start, host):
+    if not _is_port_in_use(start, host):
         return start
 
     port = start
     if not auto_select:
         raise ValueError(Errors.E1050.format(port=port))
 
-    while is_port_in_use(port, host) and port < 65535:
+    while _is_port_in_use(port, host) and port < 65535:
         port += 1
 
-    if port == 65535 and is_port_in_use(port, host):
+    if port == 65535 and _is_port_in_use(port, host):
         raise ValueError(Errors.E1049.format(host=host))
 
     # if we get here, the port changed