Check this.
[http://help.sap.com/erp2005_ehp_04/helpdata/EN/f9/c30750ac7d11d39460005004580996/frameset.htm]
hi
Port is the Logical representation of communication.
There are 4 types of ports
1)TRFC
2)File
3)R/2 (ABAP/4)
4)Internet
In ALE we transfer/exchange the data (SAP Data) b/w 2 systems ie only through RFC (Transaction RFC) we communicate with the other system.we use File Port to transfer Non Sap data b/w systems.
Tcodes :
Port Creation : WE21
RFC Destination : SM59
Regards
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