Being logged out when another user logs in from different port

I am being logged out from erpnext whenever I sign in to another port (within the same IP)
whenever i sign in to site1 i am being logged out on site2 (i am using different user accounts)

can you help me what could be the problem?

@jlx thats a known issue because cookies are shared across ports. Use name based sites or use different browsers

thank you for clarifying @rheta