I'm trying to make an HTTP Request to other System.

They provided the endpoint URL which contains a Port number.


When I'm trying to make the request I facing with this ERROR:

System.CalloutException: Unable to tunnel through proxy. Proxy returns "HTTP/1.1 503 Service Unavailable"

although I have added the URL in remote sites.

I saw some solutions about this Error (Mostly on a similar error : with "HTTP/1.0 404 Not Found") - like - ask the Other system to whiteList Salesforce IPs.

  1. There are many IPs to add to the WhiteList by the other System From here: https://help.salesforce.com/articleView?id=000321501&type=1&mode=1.

This is the best practice to add to White List by IP? If it will change (Delete, Add, Update) SF will notify me about that? Can I send them URL Instead?

  1. How can I send the Port using Apex? this is my code :

            Http httpProtocol = new Http();
            HttpRequest request = new HttpRequest();
            String url = 'https://Test.com/RESTAP/BGN/PRDV/CREATE';
            String username2 = 'Name';
            String password2 = 'Passowrd';
            Blob headerValue = Blob.valueOf(username2 + ':' + password2);
            String authorizationHeader = 'BASIC ' + EncodingUtil.base64Encode(headerValue);
            request.setHeader('Authorization', authorizationHeader);
            request.setHeader('proxyHost','PROXYHOST URL');
            HttpResponse response = httpProtocol.send(request);

I tried to send the port via HEADER like above and via change the URL to :

String URL = 'https://Test.com:50001/RESTAP/BGN/PRDV/CREATE'; 

But the error keeps coming.

Is there another thing I need to consider except ask the other System to add SF to the whiteList?


  • Are you getting this error in the response from the external system? Can you post the full stack trace from Apex Exception (or) full response?
    – Cloud Man
    Commented Jul 28, 2019 at 3:53
  • Hi @SFNinja. I'm getting this error : EXCEPTION_THROWN|[44]|System.CalloutException: Unable to tunnel through proxy. Proxy returns "HTTP/1.1 503 Service Unavailable" I Think that it came from some permission in the external service, But I gave them my URL for whitlist - but it this error is kep coming. URL : my-sandbox.cs108.my.salesforce.com I gave them only my-sandbox.
    – Salvation
    Commented Jul 31, 2019 at 11:38
  • Is the external system receiving the request sent by Salesforce? or may be it is getting blocked at firewall level or any application api gateway?
    – Cloud Man
    Commented Aug 1, 2019 at 15:42
  • Hi, I sorry for the delay. I don't think they get the request - because the response should have some value if it was. From postman it works perfectly.
    – Salvation
    Commented Aug 27, 2019 at 9:18

1 Answer 1


This URL looks like the one accessible only within company's network.

Ideally, your integration endpoint should be something which is accessible over internet since Salesforce integration calls are over internet.

  • Hi Ninja, you right. The other System First told me it assessable from any network and that why I insisted... Probably talked to the wrong people there. Thanks for your answer and sorry for the delay.
    – Salvation
    Commented Nov 14, 2019 at 10:52

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