Bind api server port before starting engine

vllm/entrypoints/openai/api_server.py

@@ -4,6 +4,7 @@
 import multiprocessing
 import os
 import re
+import socket
 import tempfile
 from argparse import Namespace
 from contextlib import asynccontextmanager
@@ -495,13 +496,18 @@ async def run_server(args, **uvicorn_kwargs) -> None:
     logger.info("vLLM API server version %s", VLLM_VERSION)
     logger.info("args: %s", args)
 
+    temp_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    temp_socket.bind(("", args.port))
+
     async with build_async_engine_client(args) as async_engine_client:
         # If None, creation of the client failed and we exit.
         if async_engine_client is None:
             return
 
         app = await init_app(async_engine_client, args)
 
+        temp_socket.close()
+
         shutdown_task = await serve_http(
             app,
             engine=async_engine_client,