CatLink/Api/InfoController.cs

using Microsoft.AspNetCore.Mvc;
using System.Text.Json.Serialization;

namespace CatLink.Api
{
    public class RelayInfoResponse
    {
        [JsonPropertyName("relayHost")]
        public string RelayHost { get; set; } = string.Empty;

        [JsonPropertyName("relayPort")]
        public int RelayPort { get; set; }
    }

    [ApiController]
    [Route("info")]
    public class InfoController : ControllerBase
    {
        private readonly IConfiguration _configuration;

        public InfoController(IConfiguration configuration)
        {
            _configuration = configuration;
        }

        [HttpGet]
        public IActionResult GetInfo()
        {
            var host = _configuration.GetValue<string>("Host") ?? "localhost";
            var relayPort = _configuration.GetValue<int>("RelayPort");

            return Ok(new RelayInfoResponse
            {
                RelayHost = host,
                RelayPort = relayPort
            });
        }
    }
}