Protocol.connect() can automatically call Transport.start()

src/cli.ts

@@ -32,16 +32,13 @@ async function runClient(url_or_command: string, args: string[]) {
 
   if (url?.protocol === "http:" || url?.protocol === "https:") {
     clientTransport = new SSEClientTransport(new URL(url_or_command));
-    await clientTransport.start();
   } else if (url?.protocol === "ws:" || url?.protocol === "wss:") {
     clientTransport = new WebSocketClientTransport(new URL(url_or_command));
-    await clientTransport.start();
   } else {
     clientTransport = new StdioClientTransport({
       command: url_or_command,
       args,
     });
-    await clientTransport.start();
   }
 
   console.log("Connected to server.");
@@ -75,7 +72,6 @@ async function runServer(port: number | null) {
         servers = servers.filter((s) => s !== server);
       };
 
-      await transport.start();
       await server.connect(transport);
     });
 
@@ -104,7 +100,6 @@ async function runServer(port: number | null) {
     });
 
     const transport = new StdioServerTransport();
-    await transport.start();
     await server.connect(transport);
 
     console.log("Server running on stdio");

src/shared/protocol.ts

@@ -83,7 +83,7 @@ export class Protocol<
   }
 
   /**
-   * Attaches to the given transport and starts listening for messages.
+   * Attaches to the given transport, starts it, and starts listening for messages.
    *
    * The Protocol object assumes ownership of the Transport, replacing any callbacks that have already been set, and expects that it is the only user of the Transport instance going forward.
    */
@@ -106,6 +106,8 @@ export class Protocol<
         this._onnotification(message);
       }
     };
+
+    await this._transport.start();
   }
 
   private _onclose(): void {

src/shared/transport.ts

@@ -8,6 +8,8 @@ export interface Transport {
    * Starts processing messages on the transport, including any connection steps that might need to be taken.
    *
    * This method should only be called after callbacks are installed, or else messages may be lost.
+   *
+   * NOTE: This method should not be called explicitly when using Client, Server, or Protocol classes, as they will implicitly call start().
    */
   start(): Promise<void>;