iOS CFSocket and C Socket - ios

Question

in iOS CFSocket the way handle callback function is as followed
void receiveData(CFSocketRef s,
CFSocketCallBackType type,
CFDataRef address,
const void *data,
void *info)
{
}
int main ()
{
CFSocketRef s = CFSocketCreate(NULL, PF_INET,
SOCK_STREAM, IPPROTO_TCP,
kCFSocketDataCallBack,
receiveData,
NULL);
struct sockaddr_in sin;
struct hostent *host;
host = gethostbyname("localhost");
memset(&sin, 0, sizeof(sin));
memcpy(&(sin.sin_addr), host->h_addr,host->h_length);
sin.sin_family = AF_INET;
sin.sin_port = htons(888);
CFDataRef address, data;
UInt8 message[] = "Hello world";
CFRunLoopSourceRef source;
address = CFDataCreate(NULL, (UInt8 *)&sin, sizeof(sin));
data = CFDataCreate(NULL, message, sizeof(message));
CFSocketConnectToAddress(s, address, 0);
CFSocketSendData(s, NULL, data, 0);
}
in CFSocket when we do a CFSocketCreate we put the callback function in the SocketCreate function.
But for C Code the Socket and read from Socket is as followed.
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
error("ERROR connecting");
printf("Please enter the message: ");
bzero(buffer,256);
fgets(buffer,255,stdin);
n = write(sockfd,buffer,strlen(buffer));
if (n < 0)
error("ERROR writing to socket");
bzero(buffer,256);
n = read(sockfd,buffer,255);
I don't how to implement the callback read function inside the C Code. The callback function would be implemented every time something come into the buffer.

Answer 1

As you noted BSD sockets is not callback based, you need to poll from read to receive new data. You can call this periodically on the main thread or create a custom thread for reading data repeatedly.
CFSocket wraps BSD sockets at a higher level. It has some nice features, I believe that it automatically handles threading, and sleeps the thread until data is received. Reimplemnenting these features would not be a trivial process.
Good resources:
http://beej.us/guide/bgnet/
BSD Sockets - How to use non-blocking sockets?
http://man7.org/linux/man-pages/man2/poll.2.html