The Annoyance Filter.pdf - Fourmilab

168 POP3 PROXY SERVER CLASS DEFINITION ANNOYANCE-FILTER §201
201. We need to obtain the IP address of the server host we’re supposed to be connecting to. This
can be specified by the user either in “dotted quad” notation, for example, “192.168.82.13” or as a
fully qualified domain name such as “pop3.fourmilab.ch”. If the former case, we convert the address
to binary with inet addr , in the latter, we invoke the resolver with gethostbyname to obtain the IP
address. We do not handle IPv6 addresses at the present time.
〈 Look up address of server 201 〉 ≡
if (isdigit (serverName [0]) ∧ (serverIP = inet addr (serverName .c str ( ))) ≠
static cast〈u int32 t 〉(−1)) {
cstat = 0;
}
else {
h = gethostbyname (serverName .c str ( ));
if (h ≠ Λ) {
memcpy (&serverIP , h ⃗ h addr , sizeof serverIP );
cstat = 0;
}
else {
cerr ≪ "POP3Proxy:␣POP3␣server␣" ≪ serverName .c str ( ) ≪ "␣unknown." ≪ endl ;
close (clientSocket );
return false ;
}
}
This code is used in section 200.