how to disable Nagle algorithm on TCP connection on iPhone

Question

I'm building a socket , using

CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault,
                                       (CFStringRef) yourHostAsNSString,
                                       yourPortAsInteger,
                                       &myReadStream,
                                       &myWriteStream);

and I see that when I send a messages with "myWriteStream" it concatenate few message together and then send them. I think it happens because of the Nagle algorithm and I want to disable it. Does any one knows how to do it?

Stephenstephenie

Answer 1

No guarantee this will fix your problem, but if you want to disable the Nagle algorithm, you need to get the native socket from the stream and call setsockopt.

CFDataRef nativeSocket = CFWriteStreamCopyProperty(myWriteStream, kCFStreamPropertySocketNativeHandle);
CFSocketNativeHandle *sock = (CFSocketNativeHandle *)CFDataGetBytePtr(nativeSocket);
setsockopt(*sock, IPPROTO_TCP, TCP_NODELAY, &(int){ 1 }, sizeof(int));
CFRelease(nativeSocket);

(Shout out to Mike Ash for the compound literal trick.)

Gorlicki

+1 Great! Where did you insert this code? Right after CFStreamCreatePairWithSocketToHost I get a BAD_EXEC because the native socket is not already initiated. – Maryjomaryl

If you're working at the CFNetwork level, call CFWriteStreamOpen first. The connection doesn't exist until open of the streams is opened. If your streams are NSStreams, use -[NSStream open]. – Gorlicki

I had to #import <netinet/tcp.h> for the TCP_NODELAY define. You could of course already have this in there depending on what else you're doing. – Reamer

you'll also need to #import <netinet/in.h> for the IPPROTO_TCP` define and the setsockopt call itself – Walkup

If you're using NSStreams, you can't get the native socket directly after -[NSStream open]. You have to wait until your delegate receives NSStreamEventOpenCompleted via stream:handleEvent:. – Altman

I tried this in the delegate callback stream:handleEvent but still get nil back from WriteStreamCopyProperty ? – Metamorphosis