@Override
    public void setTransferDigest(String transferDigest) {
        this.transferDigest = transferDigest;
    }
Tracks the different connections related to a file transfer. There are two connections, the
initiator and the target and when both connections are completed the transfer can begin.
xmppserver/src/main/java/org/jivesoftware/openfire/filetransfer/proxy/DefaultProxyTransfer.java