I'm writing a GUI application that listen for traps from a specified IP address.
The application works like this: I set the IP of the peer and then I open a
SNMP session with it.
Once the session is open the application periodically checks for traps (with
snmp_select_info and select).
I can close the session and open a new session with a different (or even the
same) peer.
The problem is that the lisening with select doesn't work on the second session.
The problem is with snmp_select_info. In fact on the second session
snmp_select_info behaves like the old session is still open: snmp_select_info
returns 2 active sessions instead of 1 and in the fdset.fd_array[] there is
still the element corrisponding to the old session that is now deleted.
So later when I call select it fails and I think that's beacuse in fdset it
finds the fd of a socket that doesn't exists anymore (in fact the error i get
from select is "No such file or directory").
Could anyone please help me solve this problem?
Thanks (and excuse me if my English is not very good ^^')
This is the code for opening the session:
init_snmp("snmpapp");
SOCK_STARTUP;
netsnmp_session session, *ss;
netsnmp_transport *transport = NULL;
transport = netsnmp_tdomain_transport("udp:162", 1, "udp");
if (transport == NULL) {
wxLogError("couldn't open udp:162 -- errno %d %s", errno,
strerror(errno));
wxLogError("SNMP failure: %s", snmp_errstring(session.s_snmp_errno));
}
snmp_sess_init( &session );
//with (AgentIP->GetValue()).c_str() I take form a Text Control the IP of
the peer
session.peername = strdup((AgentIP->GetValue()).c_str());
session.version = SNMP_VERSION_1;
session.community = "public";
session.community_len = strlen(session.community);
session.local_port = 162;
//TrapListener is the functions that handles the received traps
session.callback = &TrapListener;
//Risposta is a Text Control used by the application for visualizing the
content of the trap
session.callback_magic = (void*) Risposta;
ss = snmp_add(&session, transport, NULL, NULL);
if (!ss) {
snmp_sess_perror("ack", &session);
SOCK_CLEANUP;
wxLogError("Error in opening SNMP session");
}
else {
//WxTimer1 is a Timer that every 700ms launch the listening for traps
WxTimer1->Start(700,false);
}
This is the code for the listening part:
int fds = 0, block = 0, nopsess = 0;
fd_set fdset;
struct timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = 100000;//100 ms
FD_ZERO(&fdset);
int nopsess
nopsess = snmp_select_info(&fds, &fdset, &timeout, &block);
fds = select(fds, &fdset, 0, 0, &timeout);
if (fds<0){
wxLogError("Select failed, Errore number %d: %s", errno,
strerror(errno));
}
if (fds>0){
snmp_read(&fdset);
}
if (fds==0){
snmp_timeout();
}
This is the code for closing the open session an cleaning up:
snmp_close(ss);
SOCK_CLEANUP;
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