Shen Hui wrote:
> I want to write a server program. Several clients can
> connect to it at the same time(using socket() ,SOCKET_STREAM
> and SOCKET_DGRAM).
>
> Now here is a problem. If some clients abort abmormally,
> for example, by press
> "^C" or killed by user, clients can not tell the server to
> reclaim those sockets. In this circumstance, I want the
> server know this and then close those sockets that do not
> connect with the clients any more.
>
> How can I know the status of the sockets such as "weather
> they are connected or broken" ?
For TCP (SOCK_STREAM), the server will be notified by the kernel when
the connection is closed (e.g. by killing the client).
However, this won't account for the situation where the client system
crashes while the server is waiting on input. To deal with this, use
something similar to:
int one = 1;
setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof(one));
at the server end, where `fd' is the descriptor for the socket.
For UDP (SOCK_DGRAM), there is no such thing as a connection. The
server end will have a single socket which receives all packets from
all clients.
If the server implements some notion of a `connection' internally,
i.e. resources are allocated upon receipt of the initial packet, and
retained until the client sends some kind of termination request, then
you will need to implement some sort of keepalive timer.
--
Glynn Clements <[EMAIL PROTECTED]>
