syslog-ngを起動できません

centos 7(x64)、syslog-ng v 3.5

以下は私のsyslog-ng.cfgです。

@version:3.5
@include "scl.conf"
options {
    flush_lines (0);
    time_reopen (10);
    log_fifo_size (1000);
    chain_hostnames (off);
    use_dns (no);
    use_fqdn (no);
    create_dirs (no);
    keep_hostname (yes);
};
source s_sys {
    system();
    internal();
     udp(ip(0.0.0.0) port(514));
     tcp(ip(0.0.0.0) port(514));
};

destination d_cons { file("/dev/console"); };
destination d_mesg { file("/var/log/messages"); };
destination d_auth { file("/var/log/secure"); };
destination d_mail { file("/var/log/maillog" flush_lines(10)); };
destination d_spol { file("/var/log/spooler"); };
destination d_boot { file("/var/log/boot.log"); };
destination d_cron { file("/var/log/cron"); };
destination d_kern { file("/var/log/kern"); };
destination d_mlal { usertty("*"); };

filter f_kernel     { facility(kern); };
filter f_default    { level(info..emerg) and
                        not (facility(mail)
                        or facility(authpriv) 
                        or facility(cron)); };
filter f_auth       { facility(authpriv); };
filter f_mail       { facility(mail); };
filter f_emergency  { level(emerg); };
filter f_news       { facility(uucp) or
                        (facility(news) 
                        and level(crit..emerg)); };
filter f_boot   { facility(local7); };
filter f_cron   { facility(cron); };

log { source(s_sys); filter(f_kernel); destination(d_kern); };
log { source(s_sys); filter(f_default); destination(d_mesg); };
log { source(s_sys); filter(f_auth); destination(d_auth); };
log { source(s_sys); filter(f_mail); destination(d_mail); };
log { source(s_sys); filter(f_emergency); destination(d_mlal); };
log { source(s_sys); filter(f_news); destination(d_spol); };
log { source(s_sys); filter(f_boot); destination(d_boot); };
log { source(s_sys); filter(f_cron); destination(d_cron); };
@include "/etc/syslog-ng/conf.d/*.conf"
# Custom lines added below
source s_external { 
        udp(ip(102.94.26.26) port(514));
        #unix-dgram("/dev/log");
};

destination d_ext {
file("/var/log/$HOST-$YEAR$MONTH$DAY.log" owner(root) group(root) perm(0644) create_dirs(yes));
};

log { source(s_external); destination(d_ext); };

#ミス

#systemctl restart syslog-ng
# journalctl -xe
-- Unit syslog-ng.service has failed.
-- 
-- The result is failed.
Aug 19 16:44:49 localhost.localdomain systemd[1]: Unit syslog-ng.service entered failed state.
Aug 19 16:44:49 localhost.localdomain systemd[1]: syslog-ng.service failed.
Aug 19 16:44:49 localhost.localdomain systemd[1]: syslog-ng.service holdoff time over, scheduling restart.
Aug 19 16:44:49 localhost.localdomain systemd[1]: start request repeated too quickly for syslog-ng.service
Aug 19 16:44:49 localhost.localdomain systemd[1]: Failed to start System Logger Daemon.
-- Subject: Unit syslog-ng.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit syslog-ng.service has failed.

syslog-ngserverにログを送信するクライアントlinuxserver（centos 6）にrsyslogdが実行されていて、次の行が追加されました。

 *.* @102.94.26.27:514     #ip of syslog-ng server and port