How to receive more than 1440 through the socket

I wrote two simple programs server and a client using sockets in C++ (Linux). And initially it was a sample client-server application (echo-message sending and receiving the answer). Next, I changed the client in order to implement HTTP GET (now I do not use my sample server anymore). It works, but whatever buffer size I set, the client receives only 1440 bytes. I want to receive whole page into the buffer. I think that this is concerned with the TCP properties and I should implement some kind of cycle inside my client's code to capture a开发者_C百科ll the parts of the answer. But I don't know what exactly I should do.

This is my code:

...
int bytesSent = send(sock, tmpCharArr, message.size()+1, 0);
// Wait for the answer. Receive it into the buffer defined.
int bytesRecieved = recv(sock, resultBuf, 2048*100, 0);
...

2048*100 is a buffer size and I think this is more than enough for the relatively small WEB-page used for testing. But as I mentioned, I receive only 1440 bytes.

What can I do with recv() function call to capture all the reply "parts" when the server's response is larger then 1440 bytes?

Thanks in advance.

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The buffer size is determined by factors outside your control (routers, ADSL links, IP stacks, etc.). The standard way to transmit large volumes of data is to call recv() repeatedly.

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HTTP works over TCP, and to understand the working of TCP sockets better you have to think of them as a stream rather than packets.

For further clarity, read my earlier post: recombine split TCP packet with flash sockets

As to why you receive only 1400 (or so) bytes, you have to understand MTU and Fragmentation. To sum it up, MTU (Maximum Transmission Unit) is the ability of the network to transfer a single packet of a certain maximum size. MTU of a entire network is the lowest MTU of all the routers involved. Fragmentation is splitting up of the packets if you try to send a single packet of size larger than the MTU of that network.

For a better understanding of MTU and Fragmentation, read: http://www.miislita.com/internet-engineering/ip-packet-fragmentation-tutorial.pdf

Now as for how to receive the entire page in the buffer, one alternative is to keep calling recv() and appending the data you get in a buffer, until recv() returns zero. This will work because typically a web-server will close the TCP connection after it sends you the response. However, this technique will fail to work if the web-server doesn't close the session (maybe keep-alives are configures).

Therefore, the correct solution would be to keep receiving until you have received the HTTP header. Take a peek and determine the length of the entire HTTP response (Content-Length:) and then you can keep on receiving until you have received the exact amount of bytes you were supposed to receive.