In receiving a file delivery session in which field descriptor tables (FDTs) identify Transport Objects (TOs) transmitted along with the FDTs, a receiver determines whether the files of the session have been received using a number of timers. A fragment wait timer t1 is started for each new TO declared in an FTD when that FDT is received. Each timer is cancelled when at least a fragment of the corresponding TO is received. Alternatively, a single timer is cancelled when at least a fragment of all the TOs have been received. A new object wait timer t3 is started when all the TOs declared in an FDT are received, and is cancelled when a new FDT is received. One of a number of table wait timers t2 is started whenever a TO which is not declared in any received FDT is received, and is cancelled when an FDT declaring that object is received. The file delivery session is left if any timer expires. If following expiry of a timer it is deemed that the file delivery session has almost been received fully, the session is left after a short period of time, so as to allow the session to be fully received.