... ipconfig on my mac (that s why i am sure of my ip) ...
All right, it sounds like you have a command-line window, so let's start at the most fundamental level of network diagnostics. Please post your results so that we can see what you're seeing. "It doesn't work" won't qualify as an adequate response for being able to provide further help.
You want to know the IP address and netmask of your tablet and the mac. Are they even on the same network segment? If so, then from the mac, "ping" the IP of the tablet. If you have success, then (optionally) "ping" the mac IP from the tablet if you have such rooted tools installed (e.g.
Better Terminal Emulator Pro with
BusyBox Pro). You may need to "su -" on either end to enable the necessary socket connections and path needed to "ping".
Once you've verified that the machines can "see" and communicate with each other, it's time to see what ports are open on the mac that the tablet can see, so install
NetAudit on the tablet and scan ports on the mac, from 1 to 7000 or so. This will provide some very useful information in general (especially if one has the patience to scan from 1 to 65535) but we're looking to see what ports the vnc server is actually listening on, which depends on the way you configured the vnc server.
Once you can see those open vnc server ports, then make sure the client viewer you're using is addressing the correct port.