I am currently sitting at a university task and am facing a problem that cannot be solved for me. I'm developing a TCP client which connects to a server and gets a message from there.
The client should be able to work with strings of any length and output all received characters until the server closes the connection.
My client works and with a fixed string length, I can also receive messages from e.g. djxmmx.net port 17. However, I have no idea how to map this arbitrary length.
My C knowledge is really poor, which is why I need some suggestions, ideas or tips on how to implement my problem.
Actual this is my code for receiving messages:
// receive data from the server
char server_response[512];
recv(client_socket, &server_response, sizeof(server_response), 0);
If you're going to work with input of essentially unlimited length, you will need to call recv() several times in a loop to get each succeeding section of the input. If you can deal with each section at a time, and then discard it and move onto the next section, that's one approach. If you are going to need to process all the input in one go, you're going to have to find a way of storing arbitrarily large amounts of data, probably using dynamic memory allocation.
With recv() you will probably want to loop reading content until it returns 0 indicating that the socket has performed an orderly shutdown (documentation here). That might look something like this:
char server_response[512];
ssize_t bytes_read;
while ((bytes_read = recv(client_socket, &server_response,
sizeof(server_response), 0)) > 0) {
/* do something with the data of length bytes_read
in server_response[] */
}