An increase of 32MB over a 7 hours is similar to what you might expect if the garbage collector is never being called in .Net. Specially I see the memory increase of ‘System’ is considerably higher than ‘NetworkCommsDotNet’. Since you are primarily dealing with raw byte my guess is in your much simpler solution is reusing buffers more easily. This is something that is much more difficult to achieve by default in NetworkComms.Net as it also handles the serialisation, compression and encryption of data inline where required.
I would recommend you try using NetworkComms.Net and ensure you disable the serialisaiton and compression stages, which is discussed here https://networkcomms.net/send-receive-options/. In this mode NetworkComms.Net is much higher performance in terms of RAW throughput and also memory usage. The only downside is that you are limited to sending only byte and without compression.