Abstract: A data transmission method is provided. The method includes: establishing, by a first NAT-T sub-module of a TCP server proxy module, a transmission channel with a second NAT-T sub-module of a TCP client proxy module via a NAT-T signal server; and transmitting, by a client, a data packet to a server module in the transmission channel via the TCP server proxy module and the TCP client proxy module; wherein when a first reliable transmission sub-module of the TCP server proxy module and a second reliable transmission sub-module of the TCP client proxy module receive the data packet, the first reliable transmission sub-module and the second reliable transmission sub-module detect the transmission channel and the data packet, and suitably control the transmission channel and the data packet according to a detection result so that the data packet is reliably forwarded between the client module and the server module.