If the peer calls close() or exits, without

having messed with SO_LINGER, then our

calls to read() should return 0. It is

less clear what happens to write() calls

in this case; I would expect EPIPE, not

on the next call, but the one after.

If the peer reboots, or sets l_onoff = 1,

l_linger = 0 and then closes, then we

should get ECONNRESET (eventually) from

read(), or EPIPE from write().

When write() returns EPIPE, it also

raises the SIGPIPE signal - you never

see the EPIPE error unless you

handle or ignore the signal.

If the peer remains unreachable,

we should get some other error.

Don't think that write() can legitimately

return 0. read() should return 0 on

receipt of a FIN from the peer, and on

all following calls.

So yes, you must expect read() to return 0.

As an example, suppose you are receiving

a file down a TCP link; you

might handle the return from read() like this:

rc = read(sock,buf,sizeof(buf));

if (rc > 0)

{

write(file,buf,rc);

/* error checking on file omitted */

}

else if (rc == 0)

{

close(file);

close(sock);

/* file received successfully */

}

else /* rc < 0 */

{

/* close file and delete it, since data

is not complete report error, or whatever */

}