CODEWITHSUNDEEP
c++socketstcpbinary-databandwidth
L.Joe
L.Joe

Reputation: 3

C++ limit data on tcp connection

I wrote a simple tcp/ip connection between a client and a server in localhost in c++. It sends over tcp/ip an array of unsigned char. The size of this array is the following:

unsigned char *bytes = (unsigned char*)malloc(sizeof(unsigned char)*96000000);

//array is filled

However when I write on the socket 

    n = write(sockfd,bytes,96000000);
    if(n<0){
        cout << "error writing"<< endl;
        exit(1);
    } else{
        cout << "bytes written " << n <<endl;
    }

the number of bytes written (the n variable) that the standard output prints out is 5196978 and not 96000000 as I expected. Why? is there a limit in the number of bytes that I can write in a TCP /IP connection? How can I solve this problem?

Upvotes: 0

Views: 1230

Answers (2)

Thoth
Thoth

Reputation: 314

Why?

There could be several reasons. There might be some sort of physical limitation (hardware). The client buffer could be full. Some sort of implementation limit could have been reached. Some sort of signal could have been received.

is there a limit in the number of bytes that I can write in a TCP /IP connection?

The limit is around 2^32 bytes.

how can I solve this problem?

Keep track of how much is sent with each write and keep writing until everything in the buffer has been written.

I did not add a sample as the first question could have been answered by checking the documentation for write(), the second could have been answered with a quick search and the third question has a lot of samples out there already.

Upvotes: 0

Tony Delroy
Tony Delroy

Reputation: 106236

is there a limit in the number of bytes that I can write in a TCP /IP connection? How can I solve this problem?

Yes - your TCP stack (likely part of your Operating System) won't simply let your application enqueue an arbitrary amount of data, potentially taking up absurd amounts of buffer memory outside your app. Instead, it has a limited buffer size and after that's full you're expected to loop around and enqueue more data in the buffer - by further calls to write - after some has actually been sent over the network. So - loop and resend from where the previous send stopped: if your socket's not been set non-blocking, the call will block until more buffer space is available.

Upvotes: 2

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