Windows – RDP session error: because of a protocol error (0x112f) the remote session will be disconnected

With regards to accessing RDP (Remote Desktop Protocol), I doubt you would be able to do that on Firefox. I guess the only thing I can advise you with is LogMeIn. I'm actually using it on a constant basis and it's free if you're only after the remote controlling feature. As far as I know, it works on Firefox, Google Chrome and other modern web browsers.

/*
    This script is run in the server computer from the remote computer
    to disconnect the session without locking the server computer
    and do not require UAC after the first use
*/

; self elevate 
TaskName := RunAsTask()

; get the conexion number
Conn := ActiveSession()

; close the connection
Run, %COMSPEC% /c TSCON %Conn% /dest:console


; functions

RunAsTask() {                         ;  By SKAN,  http://ahkscript.org/boards/viewtopic.php?t=4334

  Local CmdLine, TaskName, TaskExists, XML, TaskSchd, TaskRoot, RunAsTask
  Local TASK_CREATE := 0x2,  TASK_LOGON_INTERACTIVE_TOKEN := 3 

  Try TaskSchd  := ComObjCreate( "Schedule.Service" ),    TaskSchd.Connect()
    , TaskRoot  := TaskSchd.GetFolder( "\" )
  Catch
      Return "", ErrorLevel := 1    

  CmdLine       := ( A_IsCompiled ? "" : """"  A_AhkPath """" )  A_Space  ( """" A_ScriptFullpath """"  )
  TaskName      := "[RunAsTask] " A_ScriptName " @" SubStr( "000000000"  DllCall( "NTDLL\RtlComputeCrc32"
                   , "Int",0, "WStr",CmdLine, "UInt",StrLen( CmdLine ) * 2, "UInt" ), -9 )

  Try RunAsTask := TaskRoot.GetTask( TaskName )
  TaskExists    := ! A_LastError 

  If ( not A_IsAdmin and TaskExists )      { 

    RunAsTask.Run( "" )
    ExitApp

  }

  If ( not A_IsAdmin and not TaskExists )  { 

    Run *RunAs %CmdLine%, %A_ScriptDir%, UseErrorLevel
    ExitApp

  }

  If ( A_IsAdmin and not TaskExists )      {  

    XML := "
    ( LTrim Join
      <?xml version=""1.0"" ?><Task xmlns=""http://schemas.microsoft.com/windows/2004/02/mit/task""><Regi
      strationInfo /><Triggers /><Principals><Principal id=""Author""><LogonType>InteractiveToken</LogonT
      ype><RunLevel>HighestAvailable</RunLevel></Principal></Principals><Settings><MultipleInstancesPolic
      y>Parallel</MultipleInstancesPolicy><DisallowStartIfOnBatteries>false</DisallowStartIfOnBatteries><
      StopIfGoingOnBatteries>false</StopIfGoingOnBatteries><AllowHardTerminate>false</AllowHardTerminate>
      <StartWhenAvailable>false</StartWhenAvailable><RunOnlyIfNetworkAvailable>false</RunOnlyIfNetworkAva
      ilable><IdleSettings><StopOnIdleEnd>true</StopOnIdleEnd><RestartOnIdle>false</RestartOnIdle></IdleS
      ettings><AllowStartOnDemand>true</AllowStartOnDemand><Enabled>true</Enabled><Hidden>false</Hidden><
      RunOnlyIfIdle>false</RunOnlyIfIdle><DisallowStartOnRemoteAppSession>false</DisallowStartOnRemoteApp
      Session><UseUnifiedSchedulingEngine>false</UseUnifiedSchedulingEngine><WakeToRun>false</WakeToRun><
      ExecutionTimeLimit>PT0S</ExecutionTimeLimit></Settings><Actions Context=""Author""><Exec>
      <Command>"   (  A_IsCompiled ? A_ScriptFullpath : A_AhkPath )       "</Command>
      <Arguments>" ( !A_IsCompiled ? """" A_ScriptFullpath  """" : "" )   "</Arguments>
      <WorkingDirectory>" A_ScriptDir "</WorkingDirectory></Exec></Actions></Task>
    )"    

    TaskRoot.RegisterTask( TaskName, XML, TASK_CREATE, "", "", TASK_LOGON_INTERACTIVE_TOKEN )
  }         
Return TaskName, ErrorLevel := 0
}

ActiveSession() {
    if ((wtsapi32 := DllCall("LoadLibrary", "Str", "wtsapi32.dll", "Ptr")))
    {
        if (DllCall("wtsapi32\WTSEnumerateSessionsEx", "Ptr", WTS_CURRENT_SERVER_HANDLE := 0, "UInt*", 1, "UInt", 0, "Ptr*", pSessionInfo, "UInt*", wtsSessionCount)) 
        {
            WTS_CONNECTSTATE_CLASS := {0: "WTSActive", 1: "WTSConnected", 2: "WTSConnectQuery", 3: "WTSShadow", 4: "WTSDisconnected", 5: "WTSIdle", 6: "WTSListen", 7: "WTSReset", 8: "WTSDown", 9: "WTSInit"}
            cbWTS_SESSION_INFO_1 := A_PtrSize == 8 ? 56 : 32
            Loop % wtsSessionCount {
                currSessOffset := cbWTS_SESSION_INFO_1 * (A_Index - 1)
                ExecEnvId := NumGet(pSessionInfo+0, currSessOffset, "UInt")
                currSessOffset += 4
                State := NumGet(pSessionInfo+0, currSessOffset, "UInt")
                currSessOffset += 4
                SessionId := NumGet(pSessionInfo+0, currSessOffset, "UInt")
                currSessOffset += A_PtrSize
                SessionName := StrGet(NumGet(pSessionInfo+0, currSessOffset, "Ptr"),, A_IsUnicode ? "UTF-16" : "CP0")
                currSessOffset += A_PtrSize
                HostName := StrGet(NumGet(pSessionInfo+0, currSessOffset, "Ptr"),, A_IsUnicode ? "UTF-16" : "CP0")
                currSessOffset += A_PtrSize
                UserName := StrGet(NumGet(pSessionInfo+0, currSessOffset, "Ptr"),, A_IsUnicode ? "UTF-16" : "CP0")
                currSessOffset += A_PtrSize
                DomainName := StrGet(NumGet(pSessionInfo+0, currSessOffset, "Ptr"),, A_IsUnicode ? "UTF-16" : "CP0")
                currSessOffset += A_PtrSize
                FarmName := StrGet(NumGet(pSessionInfo+0, currSessOffset, "Ptr"),, A_IsUnicode ? "UTF-16" : "CP0")

                ; MsgBox % "Username: " . UserName . "`r`n" . "State: " . WTS_CONNECTSTATE_CLASS[State] . " (raw state: " . State . ")"

                If (UserName = A_UserName && State = 0)
                    Activa := SessionId
            }
            DllCall("wtsapi32\WTSFreeMemoryEx", "UInt", WTSTypeSessionInfoLevel1 := 2, "Ptr", pSessionInfo, "UInt", wtsSessionCount)
        }
        DllCall("FreeLibrary", "Ptr", wtsapi32)
    }
    Return Activa
}