Account and System Management : System Management : Global Settings : Setting HTTP Payloads

Setting HTTP Payloads
If you want Metasploit Pro to communicate over TCP without encryption, you can set it to use HTTP payloads. HTTP payloads are useful for client-side attacks or social engineering campaigns. They are the most reliable way to communicate with a target machine, but they do not provide any level of stealth.
For example, if a victim is behind a proxy and has to use the proxy to connect back to the attacking machine, you should enable the HTTP payload option. This ensures that Metasploit can create a connection between attacker and the victim.
1.)
Select Administration > Global Settings from the main menu.
2.)
Select payload_prefer_http from the Global Settings.
3.)