File Transfer speed

[Fuwex]

Hey all.
I made a simple file transfer program in VB.NET that sends a file chunk by chunk over the network through sockets. It works fine, but it doesn't achieve speeds higher than 881 kB/sec, which is quite low over a LAN. Well, I think the hard drive should be able to write faster than that, and I write it in the usual way, using a FileStream to write. Well, other file transfer programs can send things a lot faster, and I was thinking of something like a buffer or something. But I figured the buffer would be filled a lot faster than the file writing, thus causing a lot of memory usage. I was wondering how I could achieve higher speeds?