Initial import

src/server/stdio.ts

@@ -0,0 +1,73 @@
+import process from "node:process";
+import { Readable, Writable } from "node:stream";
+import { ReadBuffer, serializeMessage } from "../shared/stdio.js";
+import { JSONRPCMessage } from "../types/index.js";
+import { Transport } from "../shared/transport.js";
+
+/**
+ * Server transport for stdio: this communicates with a MCP client by reading from the current process' stdin and writing to stdout.
+ *
+ * This transport is only available in Node.js environments.
+ */
+export class StdioServerTransport implements Transport {
+  private _readBuffer: ReadBuffer = new ReadBuffer();
+
+  constructor(
+    private _stdin: Readable = process.stdin,
+    private _stdout: Writable = process.stdout,
+  ) {}
+
+  onclose?: () => void;
+  onerror?: (error: Error) => void;
+  onmessage?: (message: JSONRPCMessage) => void;
+
+  // Arrow functions to bind `this` properly, while maintaining function identity.
+  _ondata = (chunk: Buffer) => {
+    this._readBuffer.append(chunk);
+    this.processReadBuffer();
+  };
+  _onerror = (error: Error) => {
+    this.onerror?.(error);
+  };
+
+  /**
+   * Starts listening for messages on stdin.
+   */
+  async start(): Promise<void> {
+    this._stdin.on("data", this._ondata);
+    this._stdin.on("error", this._onerror);
+  }
+
+  private processReadBuffer() {
+    while (true) {
+      try {
+        const message = this._readBuffer.readMessage();
+        if (message === null) {
+          break;
+        }
+
+        this.onmessage?.(message);
+      } catch (error) {
+        this.onerror?.(error as Error);
+      }
+    }
+  }
+
+  async close(): Promise<void> {
+    this._stdin.off("data", this._ondata);
+    this._stdin.off("error", this._onerror);
+    this._readBuffer.clear();
+    this.onclose?.();
+  }
+
+  send(message: JSONRPCMessage): Promise<void> {
+    return new Promise((resolve) => {
+      const json = serializeMessage(message);
+      if (this._stdout.write(json)) {
+        resolve();
+      } else {
+        this._stdout.once("drain", resolve);
+      }
+    });
+  }
+}