maybe works now?

dist/main.d.ts

@@ -1,9 +1,11 @@
 /// <reference types="node" />
 /// <reference types="node" />
 import { Duplex } from "node:stream";
+type WriteCallback = (error: Error | null | undefined) => void;
 export declare class Port extends Duplex {
     constructor();
-    _read(): void;
-    _write(obj: Buffer, _encoding: any, callback: Function): void;
+    read(): any;
+    write(obj: any, encodingOrCallback?: BufferEncoding | WriteCallback, callback?: WriteCallback | undefined): boolean;
     _final(): void;
 }
+export {};

dist/main.js

@@ -1,42 +1,41 @@
 import { Bert } from "./bert.js";
 import { Duplex } from "node:stream";
 const bert = new Bert();
-let termLen;
-let termBin;
 const fakeWrite = () => undefined;
 process.stdout.write = fakeWrite;
 export class Port extends Duplex {
     constructor() {
         super({ objectMode: true });
     }
-    _read() {
-        {
-            let term;
-            if (termLen === undefined && null !== (termBin = process.stdin.read(4))) {
-                termLen = bert.bytesToInt(termBin, 4, true);
+    read() {
+        const lenBytes = process.stdin.read(4);
+        if (lenBytes) {
+            const termLen = bert.bytesToInt(lenBytes, 4, true);
+            const termBytes = process.stdin.read(termLen);
+            if (termBytes) {
+                return bert.decode(termBytes);
             }
-            if (termLen !== undefined &&
-                null !== (term = process.stdin.read(termLen))) {
-                termLen = undefined;
-                this.push(bert.decode(term));
+            else {
+                process.stderr.write(`Read should have gotten ${termLen} bytes.\n`);
+                return null;
             }
         }
+        else
+            return null;
     }
-    _write(obj, _encoding, callback) {
-        let term;
+    write(obj, encodingOrCallback, callback) {
+        const actualCallback = callback || typeof encodingOrCallback === "function" ? encodingOrCallback : undefined;
         try {
-            term = bert.encode(obj, true);
+            const term = bert.encode(obj, true);
+            const len = Buffer.alloc(4);
+            len.writeUInt32BE(term.length, 0);
+            process.stdout.write(len);
+            return process.stdout.write(term, actualCallback);
         }
         catch (error) {
-            console.error(error);
-            process.exit(1);
+            process.stderr.write(`Error writing: ${error}\n`);
+            return false;
         }
-        const len = Buffer.alloc(4);
-        len.writeUInt32BE(term.length, 0);
-        process.stdout.write = this._write;
-        process.stdout.write(len);
-        process.stdout.write(term, callback);
-        process.stdout.write = fakeWrite;
     }
     // When all the data is done passing, it stops.
     _final() {

src/main.ts

@@ -3,52 +3,53 @@ import { Duplex } from "node:stream";
 
 const bert = new Bert();
 
-let termLen: number | undefined;
-let termBin: Buffer;
-
 const fakeWrite = () => undefined;
 process.stdout.write = fakeWrite as any;
 
+type WriteCallback = (error: Error | null | undefined) => void;
+
 export class Port extends Duplex {
-  constructor() {
-    super({ objectMode: true });
-  }
-
-  _read() {
-    {
-      let term;
-      if (termLen === undefined && null !== (termBin = process.stdin.read(4))) {
-        termLen = bert.bytesToInt(termBin, 4, true);
-      }
-      if (
-        termLen !== undefined &&
-        null !== (term = process.stdin.read(termLen))
-      ) {
-        termLen = undefined;
-        this.push(bert.decode(term));
-      }
+    constructor() {
+        super({ objectMode: true });
     }
-  }
 
-  _write(obj: Buffer, _encoding: any, callback: Function) {
-    let term: Buffer;
-    try {
-      term = bert.encode(obj, true);
-    } catch (error) {
-      console.error(error);
-      process.exit(1);
+    read() {
+        const lenBytes = process.stdin.read(4);
+        if (lenBytes) {
+            const termLen = bert.bytesToInt(lenBytes, 4, true);
+            const termBytes = process.stdin.read(termLen);
+
+            if (termBytes) {
+                return bert.decode(termBytes);
+            }
+            else {
+                process.stderr.write(`Read should have gotten ${termLen} bytes.\n`);
+                return null
+            }
+        }
+        else return null;
     }
-    const len = Buffer.alloc(4);
-    len.writeUInt32BE(term.length, 0);
-    process.stdout.write = this._write as any;
-    process.stdout.write(len);
-    process.stdout.write(term, callback as any);
-    process.stdout.write = fakeWrite as any;
-  }
 
-  // When all the data is done passing, it stops.
-  _final() {
-    this.push(null);
-  }
+    write(obj: any, encodingOrCallback?: BufferEncoding | WriteCallback, callback?: WriteCallback | undefined) {
+        const actualCallback: any = callback || typeof encodingOrCallback === "function" ? encodingOrCallback : undefined;
+        
+        try {
+            const term = bert.encode(obj, true);
+            const len = Buffer.alloc(4);
+            len.writeUInt32BE(term.length, 0);
+
+            process.stdout.write(len);
+            return process.stdout.write(term, actualCallback);
+        }
+        catch (error) {
+            process.stderr.write(`Error writing: ${error}\n`);
+            return false;
+        }
+    }
+
+    // When all the data is done passing, it stops.
+    _final() {
+        this.push(null);
+    }
 }