Company performance test base station, base station ordinary light cat access, mobile phone registered to the base station, mobile phone open hot spots, laptop wifi test, on a company's public IP 21 port mapping to the network on the FTP server, found no problem signaling process, but the laptop open FTP active mode, the FTP server - the data connection syn, has not yet received the laptop syn + ack, timeout retransmission, RST release connection.
Notebook after adopting passive mode, caught on the server, notebook from the FTP - syn of data, the server side has issued the syn + ack through a router, but laptop client side caught not received, the syn messages in retransmission, unable to transfer files,
Can you tell me what could be the cause?