check if ftp port is open

ftp is using port 21 to check if ftp port is open inside your network try to connect to
public ftp servers like ftp.mozilla.org and port 21 like on screenshot below.

ldap port test

LDAP is using 636 port.To verify ldap connection availability with porttester.
Specify name of the ldap server and 636 as port and click on test.

facebook chat port

to verify if facebook chat is open/avaible from your network with porttester
specify chat.facebook.com as server and 5222 as port.
Application will make attempt to connect to server and will display "Port Available" if connection is possible.
Also you can use Pidgin to connect to facebook chat.

verify if port is open

to see if port is open from inside network it's required to have outside server with port available.
For example if i want to check if port 80 is open
I can use porttest and set google.com as server name and 80 as port.

see if port is in use

PortTest application the easies way to see if port is in use for local computer or remote computer.
If you are testing local computer type localhost or 127.0.0.1 in computer text field.

Port 88

Port 88 belongs to Kerberos protocol -
this is strong authentication protocol dsigned on secret key technology.
Used for client/server authentication.
Normally this port is closed on windows machine, however some commercial
applications using this protocol.

If you have this port open that means most likely you have Kerberos
server installed on your computer.

port 123

port 123 is for Time Protocol and used for time synchronisation between server and workstations and applications.
Available on Linux, BSD, Mac OS X, Solaris and AIX and from Windows Server 2003 available on windows servers.
More detailed specification of data transmitting by this port can be found on this RFC document .