see the sql server port code example

Example 1: sql server check port number

USE master
GO
xp_readerrorlog 0, 1, N'Server is listening on' 
GO

#LogDate	ProcessInfo	Text
#...		Server		Server is listening on [ ::1 <ipv6> 1434].
#2..		Server		Server is listening on [ 127.0.0.1 <ipv4> 1434].

Example 2: sql server port number

By default SQL Server listens on TCP port number 1433, but for named instances the TCP port is dynamically configured. There are several options available to get the listening port for a SQL Server named instance.