I see two potential ways to interpret your question:
1) You could mean a redirect instead of a "rewrite" (a web server term). You want to show the domain, not the IP to the client. That's a redirect.
server { listen 123.123.123.123:6000; return 301 https://my.domain.com$request_uri; } 2) You could mean that traffic from there goes to a specific backend server. Again, I don't think you mean rewriting.
server { listen 123.123.123.123:6000; location / { proxy_pass http://my.domain.com; proxy_http_version 1.1; proxy_set_header Connection "Keep-Alive"; proxy_set_header Proxy-Connection "Keep-Alive"; } } To be more complete, perhaps you already have content for / and you only want some/path to be served by the other server:
server { listen 123.123.123.123:6000; location ~ /some/path { proxy_pass http://my.domain.com; proxy_http_version 1.1; proxy_set_header Connection "Keep-Alive"; proxy_set_header Proxy-Connection "Keep-Alive"; } location / { proxy_pass http://123.123.123.123:80; proxy_http_version 1.1; proxy_set_header Connection "Keep-Alive"; proxy_set_header Proxy-Connection "Keep-Alive"; } } This last one is a common technique to expose multiple micro-service systems as one, thus unifying the domain and simplifying SSL. In my case, I often map anything with _ to my Elasticsearch cluster.