Como encontrar a porta adequada para NSNetService no iOS?

Question

Estou criando um aplicativo com dois componentes, um componente para iPhone e um componente para Mac.Eles deveriam se comunicar via bonjour.Eu uso o seguinte código no Mac para encontrar uma porta para o serviço:

NSSocketPort *socket = [[NSSocketPort alloc] init];
struct sockaddr *addr = (struct sockaddr *)[[socket address] bytes];
int port = 9876;
if(addr->sa_family == AF_INET) {
    port = ntohs(((struct sockaddr_in *)addr)->sin_port);
} else if(addr->sa_family == AF_INET6) {
    port = ntohs(((struct sockaddr_in6 *)addr)->sin6_port);
} else {
    [socket release];
    socket = nil;
    NSLog(@"The family is neither IPv4 nor IPv6. Can't handle!!!");
}

Também posso usar esse código no iPhone e executar o aplicativo no simulador, e a conexão funciona bem.No entanto, quando tentei executar esse código em um iPhone real, descobri que NSocketPort não está disponível no iPhone.Quando tento iniciar o serviço com a porta 9876, o aplicativo Mac exibe um erro de conexão recusada quando tento conectar-me a ele.Então, como posso encontrar uma porta para usar sem usar o NSocketPort?

Answer 1

Ok, olhei o código WiTap da Apple e modifiquei-o ligeiramente para escrever um método para obter uma porta:

- (int) getPort {
CFSocketContext socketCtxt = {0, self, NULL, NULL, NULL};   

// Start by trying to do everything with IPv6.  This will work for both IPv4 and IPv6 clients 
// via the miracle of mapped IPv4 addresses.    

CFSocketRef witap_socket = CFSocketCreate(kCFAllocatorDefault, PF_INET6, SOCK_STREAM, IPPROTO_TCP, kCFSocketAcceptCallBack, nil, &socketCtxt);
uint32_t protocolFamily;

if (witap_socket != NULL)   // the socket was created successfully
{
    protocolFamily = PF_INET6;
} else // there was an error creating the IPv6 socket - could be running under iOS 3.x
{
    witap_socket = CFSocketCreate(kCFAllocatorDefault, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketAcceptCallBack, nil, &socketCtxt);
    if (witap_socket != NULL)
    {
        protocolFamily = PF_INET;
    }
}

/*if (NULL == witap_socket) {
    if (error) *error = [[NSError alloc] initWithDomain:TCPServerErrorDomain code:kTCPServerNoSocketsAvailable userInfo:nil];
    if (witap_socket) CFRelease(witap_socket);
    witap_socket = NULL;
    return NO;
}*/


int yes = 1;
setsockopt(CFSocketGetNative(witap_socket), SOL_SOCKET, SO_REUSEADDR, (void *)&yes, sizeof(yes));

// set up the IP endpoint; use port 0, so the kernel will choose an arbitrary port for us, which will be advertised using Bonjour
if (protocolFamily == PF_INET6)
{
    struct sockaddr_in6 addr6;
    memset(&addr6, 0, sizeof(addr6));
    addr6.sin6_len = sizeof(addr6);
    addr6.sin6_family = AF_INET6;
    addr6.sin6_port = 0;
    addr6.sin6_flowinfo = 0;
    addr6.sin6_addr = in6addr_any;
    NSData *address6 = [NSData dataWithBytes:&addr6 length:sizeof(addr6)];

    CFSocketSetAddress(witap_socket, (CFDataRef)address6);
    /*if (kCFSocketSuccess != CFSocketSetAddress(witap_socket, (CFDataRef)address6)) {
        if (error) *error = [[NSError alloc] initWithDomain:TCPServerErrorDomain code:kTCPServerCouldNotBindToIPv6Address userInfo:nil];
        if (witap_socket) CFRelease(witap_socket);
        witap_socket = NULL;
        return NO;
    }*/

    // now that the binding was successful, we get the port number 
    // -- we will need it for the NSNetService
    NSData *addr = [(NSData *)CFSocketCopyAddress(witap_socket) autorelease];
    memcpy(&addr6, [addr bytes], [addr length]);
    return ntohs(addr6.sin6_port);

} else {
    struct sockaddr_in addr4;
    memset(&addr4, 0, sizeof(addr4));
    addr4.sin_len = sizeof(addr4);
    addr4.sin_family = AF_INET;
    addr4.sin_port = 0;
    addr4.sin_addr.s_addr = htonl(INADDR_ANY);
    NSData *address4 = [NSData dataWithBytes:&addr4 length:sizeof(addr4)];

    CFSocketSetAddress(witap_socket, (CFDataRef)address4);
    /*if (kCFSocketSuccess != CFSocketSetAddress(witap_socket, (CFDataRef)address4)) {
        if (error) *error = [[NSError alloc] initWithDomain:TCPServerErrorDomain code:kTCPServerCouldNotBindToIPv4Address userInfo:nil];
        if (witap_socket) CFRelease(witap_socket);
        witap_socket = NULL;
        return NO;
    }*/

    // now that the binding was successful, we get the port number 
    // -- we will need it for the NSNetService
    NSData *addr = [(NSData *)CFSocketCopyAddress(witap_socket) autorelease];
    memcpy(&addr4, [addr bytes], [addr length]);
    return ntohs(addr4.sin_port);
}

}

Retirei muitos erros, então provavelmente não é o ideal, mas funciona.

Answer 2

A partir do iOS 7, o NSNetService pode criar e vincular o soquete para você.Se inicializado com porta zero, escolherá uma porta aleatória:

NSNetService *service = [[NSNetService alloc] initWithDomain:@"local." type:@"_test._tcp." name:@"Test Service" port:0];
[service publishWithOptions:NSNetServiceListenForConnections];

O serviço enviará netService:didAcceptConnectionWithInputStream:outputStream: ao seu delegado quando uma conexão for estabelecida.