| Value | Meaning |
|---|---|
| http | added in 7.10, new in 7.19.4 default is to use CONNECT HTTP/1.1 |
| http_1_0 | added in 7.19.4, force to use CONNECT HTTP/1.0 |
| socks44 | support added in 7.15.2, enum existed already in 7.10 |
| socks55 | added in 7.10 |
| socks4a6 | added in 7.18.0 |
| socks5_hostname7 | Use the SOCKS5 protocol but pass along the host name rather than the IP address. added in 7.18.0 |