[serve] Better validation for arguments to client.start() (#14327)

python/ray/serve/http_proxy.py

@@ -211,7 +211,14 @@ class HTTPProxyActor:
         sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
         if hasattr(socket, "SO_REUSEPORT"):
             sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
-        sock.bind((self.host, self.port))
+
+        try:
+            sock.bind((self.host, self.port))
+        except OSError:
+            # The OS failed to bind a socket to the given host and port.
+            raise ValueError(
+                f"""Failed to bind Ray Serve HTTP proxy to '{self.host}:{self.port}'.
+Please make sure your http-host and http-port are specified correctly.""")
 
         # Note(simon): we have to use lower level uvicorn Config and Server
         # class because we want to run the server as a coroutine. The only

python/ray/serve/tests/test_standalone.py

@@ -162,7 +162,7 @@ def test_middleware():
 
 def test_http_proxy_fail_loudly():
     # Test that if the http server fail to start, serve.start should fail.
-    with pytest.raises(socket.gaierror):
+    with pytest.raises(ValueError):
         serve.start(http_options={"host": "bad.ip.address"})
 
     ray.shutdown()