RADIUS attribute from rfc2865

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Login-TCP-Port

This Attribute indicates the TCP port with which the user is to be
      connected, when the Login-Service Attribute is also present.  It
      is only used in Access-Accept packets.

   A summary of the Login-TCP-Port Attribute format is shown below.  The
   fields are transmitted from left to right.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |             Value
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      16 for Login-TCP-Port.

   Length

      6

   Value

      The Value field is four octets.  Despite the size of the field,
      values range from 0 to 65535.

        FreeRADIUS Vendor-Specific dictionary values:

                    23 - Telnet 
                    513 - Rlogin 
                    514 - Rsh 
            

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