Sorry, we do not currently offer async method variants that would accept the CancellationToken.
However, there is the Sftp.AbortTransfer(object state) accepting object state (that you can also feed to the Sftp client async methods). Based on this you can filter the async operations to be aborted.
UPDATE:
Since release 2015R4 value types can also be used as "state".
Please note that only object types can currently be used as "state" (value types are not supported yet).
Here is a short code example showing how to use the state to abort selected async transfers:
Sftp sftp = new Sftp();
sftp.Connect("server");
sftp.Login("user", "password");
Task[] tasks = new Task[10];
string abort = "abort";
string notAbort = "notAbort";
for (int i = 0; i < 10; i++)
{
string state = i.ToString();
if (i == 0 || i == 3)
tasks[i] = sftp.PutFileAsync(string.Format(@"C:\temp\file{0}.txt", i), string.Format("file{0}.txt", i), abort);
else
tasks[i] = sftp.PutFileAsync(string.Format(@"C:\temp\file{0}.txt", i), string.Format("file{0}.txt", i), notAbort);
}
// abort transfers 0 and 3
sftp.AbortTransfer(abort);
Task.WaitAll(tasks);