MT3 API: connection failed

 
I am using a demo account for my code which is based on MT3 API. I used the code one year ago with, of course, another demo account. Recently, I have had connection problem with the code. Always connection fails though the demo account works with MT4 trading station. The server and port I am using are "217.74.32.254:1950". I also tried "195.2.82.152:1950" and "66.235.184.162:1950". The account group in the API is "demoforex". Can anyone help to advise whether I have been using anything wrong? Thanks.
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