Add support for connecting via a hostname instead of IP when using supported versions of unity and unity transport.

Author: ShadauxCat

com.unity.netcode.gameobjects/Runtime/Transports/UTP/UnityTransport.cs

@@ -317,10 +317,7 @@ private static NetworkEndpoint ParseNetworkEndpoint(string ip, ushort port, bool
                 if (!NetworkEndpoint.TryParse(ip, port, out endpoint, NetworkFamily.Ipv4) &&
                     !NetworkEndpoint.TryParse(ip, port, out endpoint, NetworkFamily.Ipv6))
                 {
-                    if (!silent)
-                    {
-                        Debug.LogError($"Invalid network endpoint: {ip}:{port}.");
-                    }
+                    return default;
                 }
 
                 return endpoint;
@@ -539,11 +536,21 @@ private bool ClientBindAndConnect()
                 serverEndpoint = ConnectionData.ServerEndPoint;
             }
 
+            NetworkConnection serverConnection;
+
             // Verify the endpoint is valid before proceeding
             if (serverEndpoint.Family == NetworkFamily.Invalid)
             {
+#if HOSTNAME_RESOLUTION_AVAILABLE && UTP_TRANSPORT_2_4_ABOVE
+                // If it's not valid, try to treat it like a URL.
+                InitDriver();
+                serverConnection = m_Driver.Connect(ConnectionData.Address, ConnectionData.Port);
+                m_ServerClientId = ParseClientId(serverConnection);
+                return true;
+#else
                 Debug.LogError($"Target server network address ({ConnectionData.Address}) is {nameof(NetworkFamily.Invalid)}!");
                 return false;
+#endif
             }
 
             InitDriver();
@@ -556,7 +563,7 @@ private bool ClientBindAndConnect()
                 return false;
             }
 
-            var serverConnection = m_Driver.Connect(serverEndpoint);
+            serverConnection = m_Driver.Connect(serverEndpoint);
             m_ServerClientId = ParseClientId(serverConnection);
 
             return true;
@@ -647,7 +654,7 @@ public void SetClientRelayData(string ipAddress, ushort port, byte[] allocationI
         /// <summary>
         /// Sets IP and Port information. This will be ignored if using the Unity Relay and you should call <see cref="SetRelayServerData"/>
         /// </summary>
-        /// <param name="ipv4Address">The remote IP address (despite the name, can be an IPv6 address)</param>
+        /// <param name="ipv4Address">The remote IP address (despite the name, can be an IPv6 address or a domain name)</param>
         /// <param name="port">The remote port</param>
         /// <param name="listenAddress">The local listen address</param>
         public void SetConnectionData(string ipv4Address, ushort port, string listenAddress = null)

com.unity.netcode.gameobjects/Runtime/com.unity.netcode.runtime.asmdef

@@ -42,10 +42,20 @@
             "expression": "2.1.0",
             "define": "UTP_TRANSPORT_2_1_ABOVE"
         },
+        {
+            "name": "com.unity.transport",
+            "expression": "2.4.0",
+            "define": "UTP_TRANSPORT_2_4_ABOVE"
+        },
         {
             "name": "Unity",
             "expression": "2023",
             "define": "UNITY_DEDICATED_SERVER_ARGUMENTS_PRESENT"
+        },
+        {
+            "name": "Unity",
+            "expression": "6000.1.0a1",
+            "define": "HOSTNAME_RESOLUTION_AVAILABLE"
         }
     ]
 }