roayu wrote:

I would like to find out is there anyway that the SER server can communicate to other SIP servers?

You could use SIP for this purpose. It has turned out to work pretty well since all SIP servers implement it by design ;-)

For instance, I have an account at SER and another account at SIPserver B. I would like to call from SER to SIPserver B, and vice versa. Is it workable? Or any additional devices needed in between these 2 SIP servers? If yes, could anyone give me some clues or guide to do so.

You might want to have a look at the documents section at http://iptel.org , especially http://www.iptel.org/ser/doc/gettingstarted.

HTH, Olaf