I was also looking for this, and found it with a user 'BlankReg', hope it helps.
Go to the ‘Network > One-to-One NAT’ page.
Check the box next to ‘Enable One-to-One NAT’, and click on the ‘Apply’ button.
Click on the ‘Add…’ button. Enter the address of your server in the 'Private Range Start:' box.
Enter the Public IP address in the 'Public Range Start' box.
Enter '1' in the 'Range Length' box. Click on the 'OK' button.
Then you need to allow this traffic through the firewall rules.
Go to the ‘Firewall > Access Rules’ page. Click on the ‘Add…’ button.
Select 'Allow' Select the 'Service' that you are hosting on the server (for example 'Web (HTTP)' if the camera uses TCP port 80).
-----> If you need a custom Port! Creating a Custom Service for non-standard port (custom port number)
-go to Firewall > Services or Network > Services
-All custom services you create are listed in the Custom Services table. You can group custom services by creating a Custom Services Group for easy policy enforcement. If a protocol is not listed in the Default Services table, you can add it to the Custom Services table by clicking Add.
1. Enter the name of the service in the Name field.
2. Select the type of IP protocol from the Protocol pull-down menu.
-Enter the Port Range or IP protocol Sub Type depending on your IP protocol selection:
– For TCP and UDP protocols, specify the Port Range. You will not need to specify a Sub Type.
– On SonicWALL NSA series appliances, for ICMP, IGMP, OSPF and PIMSM protocols, select from the Sub Type pull-down menu for sub types.
– For the remaining protocols, you will not need to specify a Port Range or Sub Type.
-- Click OK. The service appears in the Custom Services table.
----->End custom entry
----->returning to the ‘Firewall > Access Rules’
For the 'Source' select '*' and '*' for the 'Address Range Begin' box. For the Destination select the interface where the server is located, and enter it's IP address in the 'Address Range Begin' and 'Address Range End' boxes. Click on the 'OK' button. That should then allow someone on the Internet to access the camera using the service you have specified in the rule.