Network Programming Issue - buffer will only send once to the server - c++

Question

I am trying to send a file to a server using socket programming. My server and client are able to connect to each other successfully however I am expecting the while loop below to go through the entire file and add it to the server. The issue I am having is that it only send the first chunk and not the rest.
On the client side I have the following:
memset(szbuffer, 0, sizeof(szbuffer)); //Initialize the buffer to zero
int file_block_size;
while ((file_block_size = fread(szbuffer, sizeof(char), 256, file)) > 0){
if (send(s, szbuffer, file_block_size, 0) < 0){
throw "Error: failed to send file";
exit(1);
} //Loop while there is still contents in the file
memset(szbuffer, 0, sizeof(szbuffer)); //Reset the buffer to zero
}
On the server side I have the following:
while (1)
{
FD_SET(s, &readfds); //always check the listener
if (!(outfds = select(infds, &readfds, NULL, NULL, tp))) {}
else if (outfds == SOCKET_ERROR) throw "failure in Select";
else if (FD_ISSET(s, &readfds)) cout << "got a connection request" << endl;
//Found a connection request, try to accept.
if ((s1 = accept(s, &ca.generic, &calen)) == INVALID_SOCKET)
throw "Couldn't accept connection\n";
//Connection request accepted.
cout << "accepted connection from " << inet_ntoa(ca.ca_in.sin_addr) << ":"
<< hex << htons(ca.ca_in.sin_port) << endl;
//Fill in szbuffer from accepted request.
while (szbuffer > 0){
if ((ibytesrecv = recv(s1, szbuffer, 256, 0)) == SOCKET_ERROR)
throw "Receive error in server program\n";
//Print reciept of successful message.
cout << "This is the message from client: " << szbuffer << endl;
File.open("test.txt", ofstream::out | ofstream::app);
File << szbuffer;
File.close();
//Send to Client the received message (echo it back).
ibufferlen = strlen(szbuffer);
if ((ibytessent = send(s1, szbuffer, ibufferlen, 0)) == SOCKET_ERROR)
throw "error in send in server program\n";
else cout << "Echo message:" << szbuffer << endl;
}
}//wait loop
} //try loop
The code above is the setup for the connection between the client and server which works great. It is in a constant while loop waiting to receive new requests. The issue is with my buffer. Once I send the first buffer over, the next one doesn't seem to go through. Does anyone know what I can do to set the server to receive more than just one buffer? I've tried a while loop but did not get any luck.

Answer 1

Your code that sends the file from the server appears to send consecutive sections of the file correctly.
Your code that appears to have the intention of receiving the file from the client performs the following steps:
1) Wait for and accept a socket.
2) Read up to 256 bytes from the socket.
3) Write those bytes back to the socket.
At this point the code appears to go back to waiting for another connection, and keeping the original connection open, and, at least based on the code you posted, obviously leaking the file descriptor.
So, the issues seems to be that the client and the server disagreeing on what should happen. The client tries to send the entire file, and doesn't read from the socket. The server reads the first 256 bytes from the socket, and writes it back to the client.
Of course, its entirely possible that portions of the code not shown implement some of the missing pieces, but there's definitely a disconnect here between what the sending side is doing, and what the receiving side is doing.

Answer 2

buffer will only send once to the server
No, your server is only reading once from the client. You have to loop, just like the sending loop does.