Since components A and B have different clocks, you cannot directly compare the send and receive times. However, you can calculate the differences separately. If diff(timeSend) == diff(timeReceive), the latencies are likely not due to network congestion or a faulty switch/NIC but rather to delays in the operation of component A. It is highly unlikely for time differences to be the same if there is a problem with the network, it could only happen if the network was always adding a constant delay for each packet transmission.
Of course, you should perform the file saving in a separate thread to prevent blocking other operations. Write to the log file periodically, for example, by flushing the log buffer to the file once per second.