What is WIP_BOPT_DIAL_MSNULLMODEM?

Hi everyone,

On WIP_Open_AT_IP_Connectivity_Development_Guide.pdf. The wip_bearerSetOpts function which sets configuration options of a bearer. I would like to know the option

WIP_BOPT_DIAL_MSNULLMODEM

Enable MS-Windows null-modem protocol

default:TRUE (only used for
WIP_BEARER_UART_PPP)

What it mean “Enable MS-Windows null-modem protocol” ?
Does it mean i can enable/disable null modem mode(using cross cable or straight cable)?
What is (“CLIENT”/“SERVER” handshake) mean?
Anyone have more detail on this?

Thank you,
yongyew