fix: correct command format

src/index.tsx

@@ -112,8 +112,12 @@ class Printer {
         await (this._connection as UsbConnection).send(command);
         break;
       case ConnectionType.NET:
-        await (this._connection as net.Socket).write(command);
-        break;
+        return new Promise((resolve, reject) => {
+          (this._connection as net.Socket).write(command, 'binary', (err) => {
+            if (err) reject(err);
+            else resolve();
+          });
+        });
       case ConnectionType.BLUETOOTH:
         await (this._connection as BlueConnection).send(command);
         break;

src/utils.ts

@@ -2,17 +2,22 @@ import { Buffer } from 'buffer';
 
 const CRLF = Buffer.from('\r\n');
 
+const COMMA = Buffer.from(',');
+
 type CommandArg = string | number | Buffer;
 
 export const buildCommand = (command: string, ...args: CommandArg[]) => {
   const buffers = [Buffer.from(`${command} `)];
-  for (const arg of args) {
+  args.forEach((arg, index) => {
+    if (index > 0) {
+      buffers.push(COMMA);
+    }
     if (Buffer.isBuffer(arg)) {
       buffers.push(arg as Buffer);
     } else {
-      buffers.push(Buffer.from(arg.toString()));
+      buffers.push(Buffer.from(String(arg)));
     }
-  }
+  });
   buffers.push(CRLF);
   // @ts-ignore TS2345
   return Buffer.concat(buffers);