diff --git a/package.json b/package.json
index 47fa35f..c476640 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@overflow/rpc-js",
-  "version": "0.0.1",
+  "version": "0.0.4",
   "description": "TypeScript library setup for multiple compilation targets using tsc and webpack",
   "main": "./bundles/index.umd.js",
   "module": "./esm5/index.js",
diff --git a/src/client/client.ts b/src/client/client.ts
index 3c51333..beb24a4 100644
--- a/src/client/client.ts
+++ b/src/client/client.ts
@@ -70,6 +70,13 @@ export abstract class Client {
     this.clientRWC.disconnect();
   }
 
+  /**
+   * connectionStatus
+   */
+  public connectionStatus(): Observable<boolean> | undefined {
+    return this.clientRWC.connectionStatus();
+  }
+
   /**
    * notify
    */
diff --git a/src/protocol/json/client.ts b/src/protocol/json/client.ts
index 5f52fbb..ddc69d6 100644
--- a/src/protocol/json/client.ts
+++ b/src/protocol/json/client.ts
@@ -20,7 +20,7 @@ export class JSONClientCodec implements ClientCodec {
       jsonrpc: version,
       method,
       params: 0 === params.length ? null : params,
-      id,
+      id: undefined !== id && 0 < id ? id : undefined,
     };
 
     return this.codecSelector.encode(JSON.stringify(req));
diff --git a/src/protocol/json/client_notification.ts b/src/protocol/json/client_notification.ts
index 712704a..b833d1a 100644
--- a/src/protocol/json/client_notification.ts
+++ b/src/protocol/json/client_notification.ts
@@ -12,7 +12,7 @@ export class JSONClientNotificationCodec implements ClientNotificationCodec {
   public method(): string {
     return this.noti.method;
   }
-  public params(): any[] | undefined {
+  public params(): string[] | undefined {
     return this.noti.params;
   }
 }
diff --git a/src/protocol/registry_codec.ts b/src/protocol/registry_codec.ts
index 2de5c4a..70b2d2e 100644
--- a/src/protocol/registry_codec.ts
+++ b/src/protocol/registry_codec.ts
@@ -1,4 +1,4 @@
 export interface RegistryCodec {
   method(): string;
-  params(): any | undefined;
+  params(): string[] | undefined;
 }