I think you’re sending the wrong stuff.
char sendstr1[] = “PASS oauth:token\r\n”;
if (!send(sock, sendstr1, sizeof(sendstr1) + 1, 0))
You should in this case be doing sizeof(sendstr1) - 1.
This is a classic c string literal. The bytes are as follows(lets just presume ascii):
PASS oauth:token\r\n\0
The sizeof will include the hidden null terminator present in an explicitly made string literal. Then you’ve added another byte off the end of the string.
The you’ve sent both that overrun byte and the null across the network. The irc servers are not expecting a null or the random byte. You send a command and you terminate it with a \r\n.