Implements several world networking meta-vars

world.address
world.port
world.url
world.internet_address

EDIT: Does some various tweaking as per Wixoa's review

DMCompiler/DMStandard/Types/World.dm

@@ -29,8 +29,8 @@
 	var/version = 0 as opendream_unimplemented
 
 	var/address
-	var/port
-	var/internet_address = "127.0.0.1" as opendream_unimplemented
+	var/port = 0
+	var/internet_address = "127.0.0.1"
 	var/url
 	var/status as opendream_unimplemented
 	var/list/params = list() as opendream_unimplemented

OpenDreamRuntime/DreamManager.Connections.cs

@@ -5,6 +5,8 @@
 using Robust.Server.Player;
 using Robust.Shared.Enums;
 using Robust.Shared.Network;
+using System.Net;
+using System.Net.Sockets;
 
 namespace OpenDreamRuntime
 {

OpenDreamRuntime/IDreamManager.cs

@@ -1,4 +1,6 @@
-using System.Linq;
+using System.Linq;
+using System.Threading.Tasks;
+using System.Net;
 using OpenDreamRuntime.Objects;
 using Robust.Server.Player;
 

OpenDreamRuntime/Objects/MetaObjects/DreamMetaObjectWorld.cs

@@ -4,13 +4,17 @@
 using Robust.Shared;
 using Robust.Shared.Configuration;
 using Robust.Shared.Timing;
+using Robust.Shared.Network;
+using System.Net;
+using System.Net.Sockets;
 
 namespace OpenDreamRuntime.Objects.MetaObjects {
     sealed class DreamMetaObjectWorld : IDreamMetaObject {
         public bool ShouldCallNew => false; // Gets called manually later
         public IDreamMetaObject? ParentType { get; set; }
 
         [Dependency] private readonly IDreamManager _dreamManager = default!;
+        [Dependency] private readonly IServerNetManager _netManager = default!;
         [Dependency] private readonly DreamResourceManager _dreamRscMan = default!;
         [Dependency] private readonly IDreamMapManager _dreamMapManager = default!;
         [Dependency] private readonly IGameTiming _gameTiming = default!;
@@ -19,6 +23,40 @@ sealed class DreamMetaObjectWorld : IDreamMetaObject {
         private ViewRange _viewRange;
 
         private double TickLag => _gameTiming.TickPeriod.TotalMilliseconds / 100;
+        /// <summary> Determines whether we try to show IPv6 or IPv4 to the user during .address and .internet_address queries.</summary>
+        private bool DisplayIPv6
+        {
+            get
+            {
+                var binds = _cfg.GetCVar(CVars.NetBindTo).Split(',');
+                foreach (var bindAddress in binds)
+                {
+                    if (!IPAddress.TryParse(bindAddress.Trim(), out var address)) // EXTREMELY unlikely since RT does this same check on network startup
+                    {
+                        continue;
+                    }
+
+                    if (address.AddressFamily == AddressFamily.InterNetworkV6)
+                    {
+                        return true;
+                    }
+                }
+                return false;
+            }
+        }
+        /// <summary> Tries to return the address of the server, as it appears over the internet. May return null.</summary>
+        private IPAddress? InternetAddress
+        {
+            get
+            {
+                NetManager? net = (NetManager?)_netManager;
+                if(net == null) // This may be the case if we're on IntegrationNetManager instead of NetManager.
+                { // If so, I don't really know how to force RT to fess up about what our IP is, since it's all hidden behind privates at time of writing.
+                    return null;
+                }
+                return net.ServerChannel?.RemoteEndPoint.Address;
+            }
+        }
 
         public DreamMetaObjectWorld() {
             IoCManager.InjectDependencies(this);
@@ -100,12 +138,30 @@ public DreamValue OnVariableGet(DreamObject dreamObject, string varName, DreamVa
                     return new DreamValue(_dreamMapManager.Size.Y);
                 case "maxz":
                     return new DreamValue(_dreamMapManager.Levels);
-                //case "address":
-                //    return new(Runtime.Server.Address.ToString());
-                //case "port":
-                //    return new(Runtime.Server.Port);
-                //case "url":
-                //    return new("opendream://" + Runtime.Server.Address + ":" + Runtime.Server.Port);
+                case "address": // By address they mean, the local address we have on the network, not on the internet.
+                    var host = Dns.GetHostEntry(Dns.GetHostName());
+                    var ipType = DisplayIPv6 ? AddressFamily.InterNetworkV6 : AddressFamily.InterNetwork;
+                    foreach (var ip in host.AddressList)
+                    {
+                        if (ip.AddressFamily == ipType)
+                        {
+                            return new DreamValue(ip.ToString());
+                        }
+                    }
+                    return DreamValue.Null;
+                case "port":
+                    return new DreamValue(_netManager.Port);
+                case "url":
+                    if (InternetAddress == null)
+                        return DreamValue.Null;
+                    return new(InternetAddress + ":" + _netManager.Port); // RIP "opendream://"
+                case "internet_address":
+                    IPAddress? address = InternetAddress;
+                    // We don't need to do any logic with DisplayIPv6 since whatever this address is,
+                    // ought to be the address that the boolean's getter is searching for anyways.
+                    if (address == null)
+                        return DreamValue.Null;
+                    return new(address.ToString());
                 case "system_type": {
                     //system_type value should match the defines in Defines.dm
                     if (Environment.OSVersion.Platform is PlatformID.Unix or PlatformID.MacOSX or PlatformID.Other) {