yes, any real world application should certainly use a dedicated application protocol with its own header and integrity checks.
the article above is to just show a basic example of how to use sockets in general.

Hello!
This is a very common misconception about tcp. tcp is a stream of bytes. You MUST have a protocol inside
our stream ala header, message, endofdata. You must linger and wait for this complete packet and THEN
return. If your server is slow you can have an alarm(1) to end the listening. But you MUST have a progocol to adhere to.
// GH

#define CHUNK_SIZE 2048
#define TO_SEC 1
#define TO_USEC 50000

int receive_basic(int s_fd) // Block on recv
{
int rcvBytes, loopRcvd = 0, totalRcvd = 0;
char chunk[CHUNK_SIZE];

struct timeval tv = {TO_SEC, TO_USEC};
setsockopt(s_fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
while(1)
{
memset(chunk, 0, CHUNK_SIZE);
if ((rcvBytes = recv(s_fd, chunk, sizeof(chunk), 0)) >\n%s\n”, rcvBytes, loopRcvd, chunk);
}
}

printf(“Exiting receive_basic(s_fd %d) with loopRcvd %d\n\n”, s_fd, loopRcvd);
return totalRcvd;
}

One should set the timeout value at least longer than the expected arrival time of the first chunk message, else the loop may break prematurely with 0 received bytes.

Does this assume that the remote server closes the socket as soon as it’s finished sending the message? As I understand, recv() only returns 0 if the socket has been closed. So this method wouldn’t work if you want to keep the connection open for a reply, right?

Genius idea. Trying this after work.

HTTPS might not work since you are expected to have a valid certificate or credentials. You can try working with an authenticity manager..

if the server does not send the size of the packet, then the program has to decide this itself whether the transfer has completed or not.
For example if the socket connection closes or no data received for a large timeout.

Simply put, its not possible to know if the transfer completed successfully or not.

year but this is not at tutorial in how to recive a known data size.

what if you want to recive from a external server, that dosent send the size of the packet?

Still playing around with your code, making changes to see how things work and what I can do with it. Playing around with headers and portions of the code to get a better feel for how it works.

Thanks again for sharing your knowledge!

Thank you!

1. Don’t forget to “#include ” for the gettimeofday() function.
2. Get rid of the declaration for “server_reply[2000]” because it is unused and will generate a warning.

There is no direct way of fetching the total response size. It has to be coded in the server and client program.

1. For example 2 consecutive newlines can indicate the end of data. So this logic has to be coded in both the server and the client. The server appends 2 newlines to the total response, and the client upon detecting such a pattern closes the connection and marks transfer complete for the application.

2. Another way is to send the total size before sending the actual response. For example server sends like this

TOTAL_SIZE=1024rnrnABCEDFGHIJKLMN…………..

So first the total size is mentioned and then after 2 newlines the actual response follows, so the client has to deal with this, either wait till 1024 bytes of data in the response part is received. For example http response send by http servers has a “content-length” value in its header which tells the total size of the response.

Both the techniques can be developed further to ensure reliable transfer of full data.

Is there any way to request an end marker or total response size from the server or would this have to be coded into the server-side program?