Make serialport optional (#590)

Signed-off-by: yaacov <[email protected]>

Author: yaacov

index.js

@@ -18,7 +18,6 @@
 /* Add bit operation functions to Buffer
  */
 require("./utils/buffer_bit")();
-const { SerialPort } = require("serialport");
 const crc16 = require("./utils/crc16");
 const modbusSerialDebug = require("debug")("modbus-serial");
 
@@ -1249,6 +1248,8 @@ require("./apis/worker")(ModbusRTU);
 module.exports = ModbusRTU;
 
 module.exports.getPorts = function getPorts() {
+    const { SerialPort } = require("serialport");
+
     return SerialPort.list();
 };
 
@@ -1262,5 +1263,7 @@ module.exports.TelnetPort = require("./ports/telnetport");
 module.exports.C701Port = require("./ports/c701port");
 
 module.exports.ServerTCP = require("./servers/servertcp");
-module.exports.ServerSerial = require("./servers/serverserial");
+try {
+    module.exports.ServerSerial = require("./servers/serverserial");
+} catch (err) { }
 module.exports.default = module.exports;