macOS Binding to a certain port

[fuzeman]

I have a script that binds to a random port for use with a Server and Client but I really need to have The Server And Client always run for example on port 5156 just a Example I dont want the Client to Bring up Other services on other Ports just port 5156 for example how will i be able to do that this is the Code i guess you must change stuff in this code cause it has Binding and Socket etc
Thanks Alot By the way im new to xcode so im just learning

Server:

- (IBAction)toggleSharing:(id)sender {

    uint16_t chosenPort;
    if(!listeningSocket) {

        // Here, create the socket from traditional BSD socket calls, and then set up an NSFileHandle with
        //that to listen for incoming connections.
        int fdForListening;
        struct sockaddr_in serverAddress;
        int namelen = sizeof(serverAddress);

        // In order to use NSFileHandle's acceptConnectionInBackgroundAndNotify method, we need to create a
        // file descriptor that is itself a socket, bind that socket, and then set it up for listening. At this
        // point, it's ready to be handed off to acceptConnectionInBackgroundAndNotify.
        if((fdForListening = socket(AF_INET, SOCK_STREAM, 0)) > 0) {
            memset(&serverAddress, 0, sizeof(serverAddress));
            serverAddress.sin_family = AF_INET;
            serverAddress.sin_addr.s_addr = htonl(INADDR_ANY);
            serverAddress.sin_port = 0;

            // Allow the kernel to choose a random port number by passing in 0 for the port.
            if (bind(fdForListening, (struct sockaddr *)&serverAddress, namelen) < 0) {
                close (fdForListening);
                return;
            }

            // Find out what port number was chosen.
            if (getsockname(fdForListening, (struct sockaddr *)&serverAddress, &namelen) < 0) {
                close(fdForListening);
                return;
            }

            chosenPort = ntohs(serverAddress.sin_port);

            // Once we're here, we know bind must have returned, so we can start the listen
            if(listen(fdForListening, 1) == 0) {
                listeningSocket = [[NSFileHandle alloc] initWithFileDescriptor:fdForListening closeOnDealloc:YES];
            }
        }
    }

And
Client:

- (void)netServiceDidResolveAddress:(NSNetService *)sender {

    if ([[sender addresses] count] > 0) {
        NSData * address;
        struct sockaddr * socketAddress;
        NSString * ipAddressString = nil;
        NSString * portString = nil;
        int socketToRemoteServer;
        char buffer[256];
        int index;

        // Iterate through addresses until we find an IPv4 address
        for (index = 0; index < [[sender addresses] count]; index++) {
            address = [[sender addresses] objectAtIndex:index];
            socketAddress = (struct sockaddr *)[address bytes];

            if (socketAddress->sa_family == AF_INET) break;
        }

        // Be sure to include <netinet/in.h> and <arpa/inet.h> or else you'll get compile errors.

        if (socketAddress) {
            switch(socketAddress->sa_family) {
                case AF_INET:
                    if (inet_ntop(AF_INET, &((struct sockaddr_in *)socketAddress)->sin_addr, buffer, sizeof(buffer))) {
                        ipAddressString = [NSString stringWithCString:buffer];
                        portString = [NSString stringWithFormat:@"%d", ntohs(((struct sockaddr_in *)socketAddress)->sin_port)];
                    }
                    
                    // Cancel the resolve now that we have an IPv4 address.
                    [sender stop];
                    [sender release];
                    serviceBeingResolved = nil;

                    break;
                case AF_INET6:
                    // PictureSharing server doesn't support IPv6
                    return;
            }
        }   

        if (ipAddressString) [ipAddressField setStringValue:ipAddressString];
        if (portString) [portField setStringValue:portString];

        socketToRemoteServer = socket(AF_INET, SOCK_STREAM, 0);
        if(socketToRemoteServer > 0) {
            NSFileHandle * remoteConnection = [[NSFileHandle alloc] initWithFileDescriptor:socketToRemoteServer closeOnDealloc:YES];
            if(remoteConnection) {
                [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(readAllTheData:) name:NSFileHandleReadToEndOfFileCompletionNotification object:remoteConnection];
                if(connect(socketToRemoteServer, (struct sockaddr *)socketAddress, sizeof(*socketAddress)) == 0) {
                    [remoteConnection readToEndOfFileInBackgroundAndNotify];
                }
            } else {
                close(socketToRemoteServer);
            }
        }
    }
}

 

[friarbayliff]

I think it's a simple matter of assigning serverAddress.sin_port to the port you want.

example:

serverAddress.sin_port = 5156;

The client is a little different (I'm a little rusty with these things), but googling something like 'c sockets' should give you plenty of resources on network programming.

 

[fuzeman]

I think it's a simple matter of assigning serverAddress.sin_port to the port you want.

example:

serverAddress.sin_port = 5156;

The client is a little different (I'm a little rusty with these things), but googling something like 'c sockets' should give you plenty of resources on network programming.

Thats what i thought tried that Server ended up on port: 9236 How will i change the port its annoying

 

[yeroen]

You need to be aware of endian issues when you're programming network sockets:

5156 in hex is 0x1424

Now watch what happens when we swap the bytes:

5156 = 0x1424 <---> 0x2414 = 9236

For port numbers, use ntohs(3) or htons(3) to swap bytes. You can read more about it here:

http://www.gnu.org/software/libtool/manual/libc/Byte-Order.html

 

[fuzeman]

I tried that but still didnt work Any Suggestions