* Re: [Bluez-devel] reading response on bluetooth socket
2006-06-25 14:32 [Bluez-devel] reading response on bluetooth socket Götz Issel
@ 2006-06-25 14:52 ` Marcel Holtmann
2006-06-26 4:00 ` Mayank Batra
1 sibling, 0 replies; 3+ messages in thread
From: Marcel Holtmann @ 2006-06-25 14:52 UTC (permalink / raw)
To: BlueZ development
Hi Goetz,
> After having set up a rfcommm connection from my notebook to a mobile phone I
> need to get the response data from the mobile device. I can read from the
> socket using 'recv()' but if no data is there at thaht moment this will block
> the process or pause my program. What I need to do is get a signal on 'data
> available' on the socket for reading or a non blocking read. I heard there is
> a function 'select()' .. but it does not seem to work or I don't understand
> it. It needs to be as simple as possible.
>
> This is what I have now:
>
> // init + declare variables
> fd_set readFds;
> struct timeval timeout;
> struct sockaddr_rc addr = { 0 };
don't do this. Use memset() instead.
> int rfcomm_sock, status;
>
> // allocate a socket
> rfcomm_sock = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
>
> // set the connection parameters (who to connect to)
> addr.rc_family = AF_BLUETOOTH;
> addr.rc_channel = (uint8_t) dest_channel;
Why do you cast here. No need in doing this. Get you declarations right.
> str2ba( dest, &addr.rc_bdaddr );
>
> // connect to server, here mobile phone
> status = connect(rfcomm_sock, (struct sockaddr *)&addr, sizeof(addr));
>
> timeout.tv_sec=5;
> timeout.tv_usec=0;
> FD_ZERO(&readFds);
> FD_SET(rfcomm_socket, &readFds);
What is it? rfcomm_sock, rfcomm_socket or rfcommsocket. Get your code
clean.
> if (select(rfcommsocket + 1, &readFds, NULL, NULL, &timeout) == 0)
> {
> printf("timed out");
> }
> else
> printf("data ready for read");
And you should check the manual page of select() or move over using
poll(). This might be a better example:
while (1) {
fd_set rset;
FD_ZERO(&rset);
FD_SET(sk, &rset);
if (select(sk + 1, &rset, NULL, NULL, NULL) < 0)
break;
if (!FD_ISSET(sk, &rset))
continue;
...
}
Regards
Marcel
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [Bluez-devel] reading response on bluetooth socket
2006-06-25 14:32 [Bluez-devel] reading response on bluetooth socket Götz Issel
2006-06-25 14:52 ` Marcel Holtmann
@ 2006-06-26 4:00 ` Mayank Batra
1 sibling, 0 replies; 3+ messages in thread
From: Mayank Batra @ 2006-06-26 4:00 UTC (permalink / raw)
To: BlueZ development
[-- Attachment #1.1: Type: text/plain, Size: 2526 bytes --]
Hi Goetz,
On 6/25/06, Götz Issel <g.issel@fh-wolfenbuettel.de> wrote:
>
> After having set up a rfcommm connection from my notebook to a mobile
> phone I
> need to get the response data from the mobile device. I can read from the
> socket using 'recv()' but if no data is there at thaht moment this will
> block
> the process or pause my program. What I need to do is get a signal on
> 'data
> available' on the socket for reading or a non blocking read. I heard there
> is
> a function 'select()' .. but it does not seem to work or I don't
> understand
> it. It needs to be as simple as possible.
This is correct. A read() will block your thread completely.
You have two options:
- Write from one thread and read from another (Doesn't sound interesting!)
- Use select
This is what I have now:
>
> // init + declare variables
> fd_set readFds;
> struct timeval timeout;
> struct sockaddr_rc addr = { 0 };
> int rfcomm_sock, status;
>
> // allocate a socket
> rfcomm_sock = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
>
> // set the connection parameters (who to connect to)
> addr.rc_family = AF_BLUETOOTH;
> addr.rc_channel = (uint8_t) dest_channel;
> str2ba( dest, &addr.rc_bdaddr );
>
> // connect to server, here mobile phone
> status = connect(rfcomm_sock, (struct sockaddr *)&addr,
> sizeof(addr));
>
> timeout.tv_sec=5;
> timeout.tv_usec=0;
> FD_ZERO(&readFds);
> FD_SET(rfcomm_socket, &readFds);
> if (select(rfcommsocket + 1, &readFds, NULL, NULL, &timeout) == 0)
> {
> printf("timed out");
> }
> else
> printf("data ready for read");
Ahh, I assume that rfcomm_sock, rfcomm_socket and rfcommsocket refer to the
same thing.
God! did the above code ever compile??
Try the following code snippet which works for me:
fd_set readfds;
FD_ZERO(&readfds);
FD_SET(rfcomm_sock, &readfds);
while(1) {
int ready = select(FD_SETSIZE, &readfds, 0, 0, 0);
if(ready == 0)
continue;
if(ready == -1 && errno != EINTR)
break;
if(FD_ISSET(rfcomm_sock, &readfds)) {
/* You've got something on rfcomm_sock, perform a read */
int size = 1024;
size = read(rfcomm_sock, &buf, 1024);//buf is a char array declared
somewhere
/* Now, you have got the data in buf, parse it for the SAP header and
send a response if required */
}
}
Hope that helps.
Regards,
Mayank
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Using Tomcat but need to do more? Need to support web services, security?
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Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
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