[ms:~] # grep tftp /etc/inetd.conf 
tftp    dgram   udp     wait    root    /usr/libexec/tftpd      tftpd -l -s /tftpboot

[ms:~] # mkdir /tftpboot
[ms:~] # cat /tftpboot/test.txt
Hello
World

[ms:~] # /etc/rc.d/inetd rcvar

[ms:~] # cat /etc/rc.conf
...
inetd_enable=YES
...

[ms:~] # /etc/rc.d/inetd start
Starting inetd.