check the firewall logs , this will state the rule that is blocking the traffic, edit the rule to allow the communication between server and client with port and protocol.

How to create a rule that applies to the entire SEP environment
Main Policies Tab
Firewall
Rules
Make a "Blank" rule
Click the "Name" field to edit  the name of the rule to describe exactly which protocol the rule applies to
Double Click the "Service" field
    Click "Add" in Service List window
    Select  the required protocol from the Protocol Drop Down
    Select  protocol you wish to manage from the Protocol Type drop down window (your network administrator should have this information)
    Select Protocol Direction
    Click "OK" to save your choices and get back to the Rules page
    Your new service is listed first and should already be "Checked" - if not, checkmark it
    Click "Okay" to get back the Rules page

Note- You can use the "Host " field to fine tune which host IPs will use the rule and to what specific destination IP addresses they  can connect to

How to create a Location Specific Non-Shared Firewall Policy rule that only applies to a specific Group
Clients Tab
Deselect "Inherit policies and settings from parent group "My Company"
Select PoliciesTab in group window
Select Location-specific Policies >> Click Firewall Policy
Select "Create Non-Shared Policy From Copy
Rules
Make a "Blank" rule
Click the "Name" field to edit  the name of the rule to describe exactly which protocol the rule applies to
Double Click the "Service" field
    Click "Add" in Service List window
    Select the required protocol from the Protocol Drop Down
    Select  protocol you wish to manage from the Protocol Type drop down window (your network administrator should have this information)
    Select Protocol Direction
    Click "OK" to save your choices and get back to the Rules page
    Your new service is listed first and should already be "Checked" - if not, checkmark it
    Click "Okay" to get back the Rules page

Could you please tell what is the version of SEP you are using ?
We have seen that with SEP RU5  ASP.net has some  issues when application and device control enabled.

Also if you are not using SEP RU5 then  you can create and exception for asp.net in the firewall rule