diff --git a/src/server/Server.ts b/src/server/Server.ts
index 1cde9d3..7937386 100644
--- a/src/server/Server.ts
+++ b/src/server/Server.ts
@@ -35,6 +35,7 @@ export default class Server {
   protected readonly logger: Console;
   private readonly _serverImpl: GRPCServerImpl;
   private readonly _server: GRPCServer;
+  #start = false;
 
   constructor(port: string = process.env.appcallback_GRPC_PORT ?? '9999',
     GRPCServerInstance?: any,
@@ -54,9 +55,10 @@ export default class Server {
   }
 
   async start(): Promise<void> {
+    if (this.#start) return;
+    this.#start = true;
     await this._bind();
     this._server.start();
-    await sleep(250);
   }
 
   async close(): Promise<void> {
diff --git a/test/unit/server/GRPCServerImpl.test.ts b/test/unit/server/GRPCServerImpl.test.ts
index 6387647..62af2e7 100644
--- a/test/unit/server/GRPCServerImpl.test.ts
+++ b/test/unit/server/GRPCServerImpl.test.ts
@@ -65,6 +65,8 @@ describe.skip('server/GRPCServerImpl.test.ts', () => {
     const serverImpl = new CustomGRPCServerImpl(pubsubConfig);
     server = new Server('9999', serverImpl);
     await server.start();
+    // start multi times should work
+    await server.start();
   });
 
   afterAll(async () => {