Error 502, trying to proxy api for my react app

I have configured my react app using _redirects to proxy my api server. The following is the code from _redirects:

/api/*  http://beta4.tongo.in/api/:splat  200
/*    /index.html   200

Everytime it hits my API server it returns a 502 without any response body
I get response header like sampled below:

date: Sun, 29 Aug 2021 21:52:15 GMT
server: Netlify
x-nf-request-id: 01FE9YB9T06X0DK7FPHVFT5HR6

Can you kindly let me know what is the issue here?
You ca try out the app at: Raj Remedies

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Hi @dhavalmshah

Is this server/endpoint accessible? I tried curl -I http://beta4.tongo.in and get no response.

Thank you, I did not mention the port is 8080. I put that in redirects and it is now filing due to CORS, but this issue is resolved.