Question

I am writing a client-server application using sockets in C++.

The protocol for communications is essentially:

1. The client connects to the server.
2. The client “sends” an ASCII command to the server.
3. The server executes the command remotely, and gets the results, and sends the results back to the client.

the results can be multiple megabytes of data. Once all the results are sent to the client, I would like the server to signal the client that it’s done.

Is the best way to closesocket(), or should it send a message that indicates to the client that there are no more results, and the client can decide whether to close the socket or not? The drawback with closing the socket is that the client will need to establish a new connection if it wants to execute another command, but the drawback of sending a message back from the server is that the client needs to scan every recv to determine if the results are done.

Which is the best practice?

Answer 1

I would take a slightly lateral approach:

• Client sends command to server
• Server send size of response and then the real response
• Client can issue new command / close connection

In this way the client knows how much to read and can decide whether to close the connection or not.