How to read from unix socket file descriptor?

[g00dnatur3]

• Version:
• Platform:
• Subsystem:

this is the code:

console.log( fs.readlinkSync('/proc/self/fd/' + fd) );

var readStream = fs.createReadStream(null, {fd: fd});

readStream.on('error', function(err) {
    console.log(err);
});
readStream.on('data', function(data) {
    console.log(data.toString());
});

this is the output:

socket:[12357]
{ Error: EAGAIN: resource temporarily unavailable, read
at Error (native) errno: -11, code: 'EAGAIN', syscall: 'read' }

I have also tried this:

var socket = new net.Socket({fd: fd});

the error i get is:

TypeError: Unsupported fd type: UNKNOWN

Now, I can write to the fd using createWriteStream (and receive data on the other end), but I am unable to read.

If i were to read this socket using this c function it will work:

ssize_t recvmsg(int sockfd, struct msghdr *msg, int flags);
documentation here: http://linux.die.net/man/2/recvmsg

But i want to know how to read from unix socket descriptor using nodejs.

Keep in mind this code:

console.log( fs.readlinkSync('/proc/self/fd/' + fd) );

produces:

socket:[12357]

So I am just trying to read a simple unix socket, I would be shocked if this is not supported in node.

that is why I am asking the question, how do i read from a unix socket descritpor in nodejs?

Thank you for any help.

[mscdex]

Where is the socket fd created? Is the socket a stream or datagram socket?

[john-bouchard]

Inside the Bluez source code.

bluez/btio/btio.c,

look for the create_io function:
static GIOChannel *create_io(gboolean server, struct set_opts *opts, GError **err)

My bluetooth connection type is RFCOMM, so if we look at the source code we see this:

        case BT_IO_RFCOMM:
                sock = socket(PF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
                if (sock < 0) {
                        ERROR_FAILED(err, "socket(STREAM, RFCOMM)", errno);
                        return NULL;
                }
                if (rfcomm_bind(sock, &opts->src,
                                        server ? opts->channel : 0, err) < 0)
                        goto failed;
                if (!rfcomm_set(sock, opts->sec_level, opts->master, err))
                        goto failed;
                break;

So I'm pretty sure it is a stream socket.

Also, you can see from the source code, Bluez is using the gio channel lib,
here is the doc for that: https://developer.gnome.org/glib/stable/glib-IO-Channels.html

Thanks for any help you may provide :)

[bnoordhuis]

Libuv, the I/O library that node.js uses, restricts its support to AF_INET/AF_INET6 and AF_UNIX for reasons of portability.

What you could do perhaps is to turn off non-blocking mode on the file descriptor with (for example) the ffi module and then wrap it with fs.createReadStream().

[g00dnatur3]

Thank you for your help + advice, thought this was the case.

Im not sure i want to have blocking io, going to try and create a gyp binding to gio-channel instead.

Cheers!