Fix various edge cases in testssl.

- Ignore SIGPIPE to work around IO::Socket::SSL having its socket
  closed from under it and terminating the program.

- Improve detection of servers that close the TCP connection right
  after it is opened. This usually means the IP address the tool is
  connecting from has been banned so suggest that as well.

- Show more debug information when a connection fails.

tools/testssl

@@ -42,6 +42,10 @@ if (scalar @ARGV < 2) {
 # needs so we disable it.
 STDOUT->autoflush(1);
 
+# If a server closes the connection whilst an SSL session is being initiated we
+# want EPIPE instead of SIGPIPE.
+$SIG{PIPE} = 'IGNORE';
+
 my $hostip = shift @ARGV;
 if ($hostip =~ /[^A-Za-z0-9.:-]/) {
 	say STDERR "Error: invalid hostname or IP address: $hostip";
@@ -73,6 +77,10 @@ It seems like the server endpoint you specified is not reachable! Make sure that
   * If you are using a firewall incoming connections on TCP port $port are allowed.
   * The endpoint your server is listening on is not local or private.
 
+The error provided by the socket library was:
+
+  $IO::Socket::errstr
+
 See https://docs.inspircd.org/3/configuration/#bind for more information.
 EOM
 	exit 1;
@@ -82,7 +90,7 @@ say "${\CC_GREEN}yes${\CC_RESET}";
 print "Checking whether ${\CC_BOLD}$hostip/$port${\CC_RESET} is using plaintext ... ";
 my $error = $sock->recv(my $data, 1);
 
-if ($error) {
+if (!defined $error || $data eq '') {
 	say <<"EOM";
 ${\CC_RED}error${\CC_RESET}
 
@@ -90,6 +98,7 @@ It seems like the server dropped the connection before sending anything! Make su
 
   * The endpoint you specified is actually your IRC server.
   * If you are using a firewall incoming data on TCP port $port are allowed.
+  * The IP address you are connecting from has not been banned from the server.
 
 See https://docs.inspircd.org/3/configuration/#bind for more information.
 EOM