diff --git a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/common/core/bin/www.ts b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/common/core/bin/www.ts
index 52444e2a5b..08df7236dc 100644
--- a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/common/core/bin/www.ts
+++ b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/common/core/bin/www.ts
@@ -69,7 +69,7 @@ server.on("listening", onListening);
  * Normalize a port into a number, string, or false.
  */
 
-function normalizePort(val) {
+function normalizePort(val: string) {
   const port = parseInt(val, 10);
 
   if (isNaN(port)) {
@@ -89,7 +89,7 @@ function normalizePort(val) {
  * Event listener for HTTPS server "error" event.
  */
 
-function onError(error) {
+function onError(error: any) {
   if (error.syscall !== "listen") {
     throw error;
   }
@@ -118,6 +118,12 @@ function onError(error) {
 
 function onListening() {
   const addr = server.address();
+
+  if (!addr) {
+    logger.error("Could not get running server address - exit.");
+    process.exit(1);
+  }
+
   const bind = typeof addr === "string" ? "pipe " + addr : "port " + addr.port;
   debug("Listening on " + bind);
 }
@@ -144,14 +150,14 @@ io.on("connection", function (client) {
     // Check for the existence of the specified function and call it if it exists.
     if (Splug.isExistFunction(func)) {
       // Can be called with Server plugin function name.
-      Splug[func](args)
-        .then((respObj) => {
+      (Splug as any)[func](args)
+        .then((respObj: unknown) => {
           logger.info("*** RESPONSE ***");
           logger.info("Client ID :" + client.id);
           logger.info("Response  :" + JSON.stringify(respObj));
           client.emit("response", respObj);
         })
-        .catch((errObj) => {
+        .catch((errObj: unknown) => {
           logger.error("*** ERROR ***");
           logger.error("Client ID :" + client.id);
           logger.error("Detail    :" + JSON.stringify(errObj));
@@ -172,11 +178,12 @@ io.on("connection", function (client) {
   // TODO: "request2" -> "request"
   client.on("request2", function (data) {
     const methodType = data.method.type;
-    // const args = data.args;
-    const args = {};
-    args["contract"] = data.contract;
-    args["method"] = data.method;
-    args["args"] = data.args;
+    let args: Record<string, any> = {
+      contract: data.contract,
+      method: data.method,
+      args: data.args,
+    };
+
     if (data.reqID !== undefined) {
       logger.info(`##add reqID: ${data.reqID}`);
       args["reqID"] = data.reqID;
@@ -223,14 +230,14 @@ io.on("connection", function (client) {
       // Check for the existence of the specified function and call it if it exists.
       if (Splug.isExistFunction(func)) {
         // Can be called with Server plugin function name.
-        Splug[func](args)
-          .then((respObj) => {
+        (Splug as any)[func](args)
+          .then((respObj: unknown) => {
             logger.info("*** RESPONSE ***");
             logger.info("Client ID :" + client.id);
             logger.info("Response  :" + JSON.stringify(respObj));
             client.emit("response", respObj);
           })
-          .catch((errObj) => {
+          .catch((errObj: unknown) => {
             logger.error("*** ERROR ***");
             logger.error("Client ID :" + client.id);
             logger.error("Detail    :" + JSON.stringify(errObj));
@@ -262,19 +269,16 @@ io.on("connection", function (client) {
    * startMonitor: starting block generation event monitoring
    **/
   client.on("startMonitor", function () {
-    // Callback to receive monitoring results
-    const cb = function (callbackData) {
+    Smonitor.startMonitor(client.id, (event) => {
       let emitType = "";
-      if (callbackData.status == 200) {
+      if (event.status == 200) {
         emitType = "eventReceived";
         logger.info("event data callbacked.");
       } else {
         emitType = "monitor_error";
       }
-      client.emit(emitType, callbackData);
-    };
-
-    Smonitor.startMonitor(client.id, cb);
+      client.emit(emitType, event);
+    });
   });
 
   /**
diff --git a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/PluginUtil.ts b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/PluginUtil.ts
index e2a554be11..f9b322ce66 100644
--- a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/PluginUtil.ts
+++ b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/PluginUtil.ts
@@ -23,7 +23,7 @@
  *         3.78*10^14
  *         3.78e14
  */
-export function convNum(value, defaultValue) {
+export function convNum(value: number | string, defaultValue: number | string) {
   let retValue = 0;
   let defValue = 0;
 
diff --git a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerMonitorPlugin.ts b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerMonitorPlugin.ts
index 51d383ae95..5684c539f9 100644
--- a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerMonitorPlugin.ts
+++ b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerMonitorPlugin.ts
@@ -25,21 +25,18 @@ import { ValidatorAuthentication } from "./ValidatorAuthentication";
 const Web3 = require("web3");
 import safeStringify from "fast-safe-stringify";
 
+export type MonitorCallback = (callback: {
+  status: number;
+  blockData?: string;
+  errorDetail?: string;
+}) => void;
+
 /*
  * ServerMonitorPlugin
  * Class definitions of server monitoring
  */
 export class ServerMonitorPlugin {
-  _filterTable: object;
-
-  /*
-   * constructors
-   */
-  constructor() {
-    // Define dependent specific settings
-    // Initialize monitored filter
-    this._filterTable = {};
-  }
+  _filterTable = new Map<string, any>();
 
   /*
    * startMonitor
@@ -47,11 +44,11 @@ export class ServerMonitorPlugin {
    * @param {string} clientId: Client ID from which monitoring start request was made
    * @param {function} cb: A callback function that receives monitoring results at any time.
    */
-  startMonitor(clientId, cb) {
+  startMonitor(clientId: string, cb: MonitorCallback) {
     logger.info("*** START MONITOR ***");
     logger.info("Client ID :" + clientId);
     // Implement handling to receive events from an end-chain and return them in a callback function
-    let filter = this._filterTable[clientId];
+    let filter = this._filterTable.get(clientId);
     if (!filter) {
       logger.info("create new web3 filter and start watching.");
       try {
@@ -63,8 +60,8 @@ export class ServerMonitorPlugin {
         filter = web3.eth.filter("latest");
         // filter should be managed by client ID
         // (You should never watch multiple urls from the same client)
-        this._filterTable[clientId] = filter;
-        filter.watch(function (error, blockHash) {
+        this._filterTable.set(clientId, filter);
+        filter.watch(function (error: any, blockHash: string) {
           if (!error) {
             console.log("##[HL-BC] Notify new block data(D2)");
             const blockData = web3.eth.getBlock(blockHash, true);
@@ -92,7 +89,7 @@ export class ServerMonitorPlugin {
           } else {
             const errObj = {
               status: 504,
-              errorDetail: error,
+              errorDetail: safeStringify(error),
             };
             cb(errObj);
           }
@@ -115,14 +112,14 @@ export class ServerMonitorPlugin {
    * monitoring stop
    * @param {string} clientId: Client ID from which monitoring stop request was made
    */
-  stopMonitor(clientId) {
+  stopMonitor(clientId: string) {
     // Implement a process to end EC monitoring
-    const filter = this._filterTable[clientId];
+    let filter = this._filterTable.get(clientId);
     if (filter) {
       // Stop the filter & Remove it from table
       logger.info("stop watching and remove filter.");
       filter.stopWatching();
-      delete this._filterTable[clientId];
+      this._filterTable.delete(clientId);
     }
   }
 }
diff --git a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerPlugin.ts b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerPlugin.ts
index bfe8b4c34c..13daf07fc0 100644
--- a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerPlugin.ts
+++ b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/src/main/typescript/connector/ServerPlugin.ts
@@ -47,8 +47,8 @@ export class ServerPlugin {
    *       Scope of this function is in this class
    *       Functions that should not be called directly should be implemented outside this class like utilities.
    */
-  isExistFunction(funcName) {
-    if (this[funcName] != undefined) {
+  isExistFunction(funcName: string) {
+    if ((this as any)[funcName]) {
       return true;
     } else {
       return false;
@@ -67,11 +67,11 @@ export class ServerPlugin {
    * }
    * @return {Object} JSON object
    */
-  getNumericBalance(args) {
+  getNumericBalance(args: any) {
     // * The Web3 API can be used synchronously, but each function is always an asynchronous specification because of the use of other APIs such as REST,
     return new Promise((resolve, reject) => {
       logger.info("getNumericBalance start");
-      let retObj = {};
+      let retObj: Record<string, any>;
 
       const referedAddress = args.args.args[0];
       const reqID = args["reqID"];
@@ -139,11 +139,11 @@ export class ServerPlugin {
    * }
    * @return {Object} JSON object
    */
-  transferNumericAsset(args) {
+  transferNumericAsset(args: any) {
     return new Promise((resolve, reject) => {
       logger.info("transferNumericAsset start");
 
-      let retObj = {};
+      let retObj: Record<string, any>;
       let sendArgs = {};
       const sendFunction = "sendTransaction";
       // const funcParam = args;
@@ -231,11 +231,11 @@ export class ServerPlugin {
    * }
    * @return {Object} JSON object
    */
-  getNonce(args) {
+  getNonce(args: any) {
     // * The Web3 API can be used synchronously, but each function is always an asynchronous specification because of the use of other APIs such as REST,
     return new Promise((resolve, reject) => {
       logger.info("getNonce start");
-      let retObj = {};
+      let retObj: Record<string, any>;
 
       const targetAddress = args.args.args.args[0];
       const reqID = args["reqID"];
@@ -316,11 +316,11 @@ export class ServerPlugin {
    * }
    * @return {Object} JSON object
    */
-  toHex(args) {
+  toHex(args: any) {
     // * The Web3 API can be used synchronously, but each function is always an asynchronous specification because of the use of other APIs such as REST,
     return new Promise((resolve, reject) => {
       logger.info("toHex start");
-      let retObj = {};
+      let retObj: Record<string, any>;
 
       const targetValue = args.args.args.args[0];
       const reqID = args["reqID"];
@@ -393,11 +393,11 @@ export class ServerPlugin {
    * }
    * @return {Object} JSON object
    */
-  sendRawTransaction(args) {
+  sendRawTransaction(args: any) {
     return new Promise((resolve, reject) => {
       logger.info("sendRawTransaction(start");
 
-      let retObj = {};
+      let retObj: Record<string, any>;
       const sendArgs = {};
       const sendFunction = "sendTransaction";
       const funcParam = args.args.args[0];
@@ -451,11 +451,11 @@ export class ServerPlugin {
    * }
    * @return {Object} JSON object
    */
-  web3Eth(args) {
+  web3Eth(args: any) {
     return new Promise((resolve, reject) => {
       logger.info("web3Eth start");
 
-      let retObj = {};
+      let retObj: Record<string, any>;
       const sendFunction = args.method.command;
       const sendArgs = args.args.args[0];
       const reqID = args["reqID"];
@@ -518,11 +518,11 @@ export class ServerPlugin {
    * }
    * @return {Object} JSON object
    */
-  contract(args) {
+  contract(args: any) {
     return new Promise((resolve, reject) => {
       logger.info("contract start");
 
-      let retObj = {};
+      let retObj: Record<string, any>;
       const sendCommand = args.method.command;
       const sendFunction = args.method.function;
       const sendArgs = args.args.args;
diff --git a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/tsconfig.json b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/tsconfig.json
index 7713871089..90eae72ba8 100644
--- a/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/tsconfig.json
+++ b/packages/cactus-plugin-ledger-connector-go-ethereum-socketio/tsconfig.json
@@ -8,7 +8,6 @@
     "emitDecoratorMetadata": true,
     "experimentalDecorators": true,
     "tsBuildInfoFile": "../../.build-cache/cactus-plugin-ledger-connector-go-ethereum-socketio.tsbuildinfo",
-    "strict": false // TODO - True, fix warnings
   },
   "include": [
     "./src/main/typescript/common/core/*.ts",