Explanation/Reference:
SQL Server provides a dedicated administrator connection (DAC). The DAC lets an administrator access a running server to execute diagnostic functions or Transact-SQL statements, or to troubleshoot problems on the server, even when the server is locked or running in an abnormal state and not responding to a SQL Server Database Engine connection. By default, the DAC is only available from a client on the server. To enable client applications on remote computers to use the DAC, use the remote admin connections option of sp_configure.
By default, the DAC only listens on the loop-back IP address (127.0.0.1), port 1434 The following example enables the DAC from a remote computer.
sp_configure 'remote admin connections', 1;
GO
RECONFIGURE;
GO
References: https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/remote-admin- connections-server-configuration-option