Initialization Index page and Web Socket Open gives an Error

Gatling (Open-Source)
1

When I’m initializing(POST INDEX PAGE) my index page, it is giving me the following error.

KO bodyString.find.transform.exists failed, could not extract: transform crashed: Unexpected character (‘2’ (code 50)): was expecting comma to separate OBJECT entries

Code:

    .exec(http("POST INDEX PAGE")
      .post("/?v-1471231389581")
//      .headers(Map("Content-Type" -> "application/json; charset=UTF-8"))
      .formParam("v-browserDetails","1")
      .formParam("theme", "mytheme")
      .formParam("v-appId", appver)
      .formParam("v-sh", "1200")
      .formParam("v-sw", "1920")
      .formParam("v-cw", "147")
      .formParam("v-ch", "1047")
      .formParam("v-curdate", "1470999686031")
      .formParam("v-tzo", "-330")
      .formParam("v-dstd", "0")
      .formParam("v-rtzo", "-330")
      .formParam("v-dston", "false")
      .formParam("v-vw", "147")
      .formParam("v-vh", "0")
      .formParam("v-loc", baseurl + "/")
      .formParam("v-wn", appver + "-0.7179318188297512")
      .check(Checker.httpChecker)
    ).pause(1 seconds)

Checker:

val httpChecker = bodyString.transform {
  (resp, session) =>
  val state = new VaadinState;
    println("\n resp :"+resp+"\n")
    println("\n session :"+session+"\n")
    println("Started user " + session.get("userName").as[String] + " " + session.get("password").as[String]);
  state.userName = session.get("userName").as[String];
  HttpRequestCreator.userStates += (session.get("userName").as[String] -> state);

  //Find and store jsessionId
  val url = new URL( new AppConfig().getBaseURL() );
  val jsessionCookie = session("gatling.http.cookies").as[CookieJar].get(Uri.create( url.getProtocol+"://" + url.getHost+url.getPath+"/")).find(_.getName == "JSESSIONID");
  state.jsessionid = jsessionCookie.getOrElse(null).getValue;
    println("\n jsession id"+state.jsessionid+"\n")
    println("\n resp :"+resp+ "\n")
  state.readJsonState(state.httpResponseToValidJsonString(resp));
}

After that I’ve tried without posting those parameters. Then the sync id of the response is giving -1 even though it says web socket is open.