Use bind to check port instead of connect_ex.

spacy/displacy/__init__.py

@@ -102,14 +102,15 @@ def serve(
 
     # automatically switch to the next available port if the default / given port is taken
     available_port = port
-    while is_port_in_use(available_port) and available_port <= 65535:
+
+    while is_port_in_use(available_port) and available_port < 65535:
         available_port += 1
 
     if is_in_jupyter():
         warnings.warn(Warnings.W011)
     render(docs, style=style, page=page, minify=minify, options=options, manual=manual)
 
-    if port > 65535:
+    if available_port == 65535 and is_port_in_use(available_port):
         raise ValueError(Errors.E1048.format(host=host))
 
     if available_port != port:

spacy/errors.py

@@ -958,7 +958,7 @@ class Errors(metaclass=ErrorsWithCodes):
     E1046 = ("{cls_name} is an abstract class and cannot be instantiated. If you are looking for spaCy's default "
              "knowledge base, use `InMemoryLookupKB`.")
     E1047 = ("`find_threshold()` only supports components with a `scorer` attribute.")
-    E1048 = ("No port available for displacy on host {host}. Please specify a port by `displacy.serve(doc, port)`.")
+    E1048 = ("No port available found for displacy on host {host}. Please specify an available port by `displacy.serve(doc, host, port)`.")
 
 
 # Deprecated model shortcuts, only used in errors and warnings

spacy/util.py

@@ -1739,5 +1739,12 @@ def all_equal(iterable):
 
 
 def is_port_in_use(port):
-    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
-        return s.connect_ex(('localhost', port)) == 0
+    """Check if localhost:port is in use."""
+    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    try:
+        s.bind(("localhost", port))
+        return False
+    except socket.error:
+        return True
+    finally:
+        s.close()