You can enter "show interface summary" to see the tx rate and rx rate for each port. Very easy to read format.
To use wireshark remotely, you could always use ERSPAN, which would send the monitor session to a remote switch. If I'm not sure of the commands I'm entering on a remote switch, I normally do a "reload in 15". In case I lose connectivity, it will reload in x number of minutes to restore service. Save you a commute to the remote site to restore service. Just don't forget to cancel the reload when you are finished.
https://supportforums.cisco.com/document/139236/understanding-spanrspanand-erspan#comment-10119266
If you have network monitoring software, it should show the top talker along with the ip address.
show arp | i x.x.xx
this will return the mac
then enter show mac address-table address xxxx.xxxx.xxxx
this will show the interface that learned the mac.
show cdp neigh to verify the port isn't connected to another switch.
Keep entering sh mac and sh cdp until you locate the port with the mac of the top talker.
You can shut the port and see if the trouble goes away.
Just be careful when shutting ports. Its easy to shut the wrong port and lose connectivity.
