I am a newbie in linux.
I am using ipmsg(courtesy wine) on opensuse 11.1,which has to interact with ipmsgs on windows,currently i have to disable firewall to get it working.
Is there any way i can use it without disabling firewall or allowing it through firewall.
Go into Yast -> Security and Users -> Firewall, select “Allowed Services,” then click the “advanced” tab. The default port # for ipmsg is 2425; enter that for both UDP and TCP (if you have to, enter it twice, once for UDP, and again for TCP – this can vary from one version to the next).
If the Windows machines are using a different port, though, you’ll have to determine what port number they’re using, then open that one in the “Advanced” firewall settings.
will it not be unsafe to open a port through firewall
Yes and no. 
A lot of this depends on whether the ipmsg service itself is secure, and I can’t answer that. I’m not that familiar with it. But with that firewall port closed (and all of them are normally closed by default), ipmsg simply won’t work. Other PCs will try to talk to your machine and there won’t be an answer, because your machine never even sees the request. It’s blocked at the firewall.
Therefore, it’s up to you: if you’re satisfied that ipmsg is a reasonably “safe” service, open the port in the firewall. I can assure you of this: running the machine without any firewall at all is a whole lot riskier (but you obviously know that).