C# ==> Asyncsocket reading buffer?

Question

I have a C# server that accepts multiple clients, and multiple messages from each client.

1- In order to start reading from each client i need to pass a buffer (bytes), but the problem is I don't know how much data is the client is going to send. So is there a way to know how much data a client is going to send so that i can start reading for the correct amount of data?

2- Is it oK if i use only 1 byte array to read from all clients? or do i need to create a byte array for reading from each client?

Answer 1

1. Unless your protocol dictates how much data will be sent, no. Typically you read one buffer's-worth and then potentially read more. It will really depend on the protocol though. If the client can only send one message on each connection, you'll typically keep reading until the next call returns 0 bytes. Otherwise either the messages have delimiters or a length-prefix.

2. Absolutely not - assuming you're going to be reading from multiple clients concurrently (why else would you use asynchronous communications?) you'd end up with the different clients' data all being written over each other. Create a new byte array for each client. Depending on exactly what you do with the data you may be able to reuse the same byte array for the next read for the same client - and you could reuse the byte array for later clients, if you really wanted... but don't read from multiple clients at the same time into the same buffer.

Answer 2

So is there a way to know how much data a client is going to send so that i can start reading for the correct amount of data?

Any protocol ought to have some mechanism for a client to indicate when it is done sending data, either as a "length" value that is sent before the actual data, or as a special terminating sequence that is sent after the data.

Is it oK if i use only 1 byte array to read from all clients? or do i need to create a byte array for reading from each client?

Depends on how your program works. If you'll have multiple simultaneous clients, obviously you can't have just a single buffer because they'll end up overwriting each other. If it's one client after the other, but only one at a time, there's no problem in having just one buffer.