This paper describes a Full-dup1ex File Transmission System which，with the support of NETBIOS，can transmit files between any two nodes in a network implemented by the task mechanism of Ada. During a transmission procedure，files are transmitted in the form of grouped datagrams. The management of receiving and sendíng processes，as well as the background full-duplex operation，are all imp1emented by the task features of Ada. The paper a1so briefly describes some techniques used in the imp1ementation.