Add DNS SRV record resolution to client direct connection

.gitignore

@@ -56,5 +56,8 @@ Barotrauma/**/GameAnalyticsKeys.cs
 Deploy/DeployAll/PrivateKey.*
 .github/ISSUE_TEMPLATE/release-checklist.md
 
-#Rider
+# Rider
 *.DotSettings.user
+
+# VSCode
+.vscode/

Barotrauma/BarotraumaShared/SharedSource/Networking/DnsSrvResolver.cs

@@ -0,0 +1,47 @@
+#nullable enable
+using DnsClient;
+using System.Linq;
+
+namespace Barotrauma.Networking
+{
+    internal static class DnsSrvResolver
+    {
+        private static readonly LookupClient lookup = new();
+        private const string Service = "_barotrauma";
+        private const string Proto = "_udp";
+
+        /// <summary>Returns true if a SRV record was found.</summary>
+        public static bool TryResolve(string host, string service, string proto, out string targetHost, out int targetPort)
+        {
+            targetHost = "";
+            targetPort = 0;
+            var queryName = $"{service}.{proto}.{host.TrimEnd('.')}";
+
+            IDnsQueryResponse result;
+            try
+            {
+                result = lookup.Query(queryName, QueryType.SRV);
+            }
+            catch
+            {
+                return false;
+            }
+
+            var record = result.Answers
+                               .SrvRecords()
+                               .OrderBy(r => r.Priority)
+                               .ThenByDescending(r => r.Weight)
+                               .FirstOrDefault();
+            if (record is null) return false;
+
+            targetHost = record.Target.Value.TrimEnd('.');
+            targetPort = record.Port;
+
+            return true;
+        }
+
+        /// <summary>Returns true if a SRV record was found.</summary>
+        public static bool TryResolve(string host, out string targetHost, out int targetPort)
+            => TryResolve(host, Service, Proto, out targetHost, out targetPort);
+    }
+}

Barotrauma/BarotraumaShared/SharedSource/Networking/Primitives/Endpoint/LidgrenEndpoint.cs

@@ -38,6 +38,15 @@ public static Option<LidgrenEndpoint> ParseFromWithHostNameCheck(string endpoint
                 port = int.TryParse(split[1], out var tmpPort) ? tmpPort : port;
             }
 
+            // SRV look-up: only when the user did not specify a port
+            if (port == NetConfig.DefaultPort
+                && tryParseHostName
+                && DnsSrvResolver.TryResolve(hostName, out var srvHost, out var srvPort))
+            {
+                hostName = srvHost;
+                port     = srvPort;
+            }
+
             if (LidgrenAddress.Parse(hostName).TryUnwrap(out var adr) || 
                 (tryParseHostName && LidgrenAddress.ParseHostName(hostName).TryUnwrap(out adr)))
             {

Barotrauma/BarotraumaTest/DnsSrvResolverTests.cs

@@ -0,0 +1,26 @@
+// Add extern alias to pick up WindowsClient reference
+extern alias Client;
+
+using System;
+using Xunit;
+
+namespace WindowsTest
+{
+    public class DnsSrvResolverTests
+    {
+        [Fact]
+        public void DefaultTryResolve_NoSrvRecord_ReturnsFalse()
+            => Assert.False(Client::Barotrauma.Networking.DnsSrvResolver.TryResolve("example.com", out _, out _));
+
+        [Fact]
+        public void OverloadedTryResolve_XmppJabber_ReturnsTrue()
+        {
+            // jabber.org provides a stable XMPP server SRV record
+            bool ok = Client::Barotrauma.Networking.DnsSrvResolver.TryResolve(
+                "jabber.org", "_xmpp-server", "_tcp", out var host, out var port);
+            Assert.True(ok, "Expected SRV record for _xmpp-server._tcp.jabber.org");
+            Assert.EndsWith("jabber.org", host);
+            Assert.True(port > 0);
+        }
+    }
+}

Libraries/BarotraumaLibs/BarotraumaCore/BarotraumaCore.csproj

@@ -23,6 +23,7 @@
 
     <ItemGroup>
       <ProjectReference Include="..\..\XNATypes\XNATypes.csproj" />
+      <PackageReference Include="DnsClient" Version="1.8.0" />
     </ItemGroup>
 
 </Project>