I wanna build a TCP/IP server that will be used by up to 100 concurrent clients, but still not sure how to get started.
at least I need the server to this:
Some excellent component sets that are useful for situations like yours (and much more) are kbmMW and RemObjects. There are some other good sets, too, I think, you could do a search of archive or ask a question in Embarcaderos' Delphi thirdpartytools newsgroup. You can search archives here: http://codenewsfast.com/