Linux tftp 命令

In my embedded platform, I want to use tftp command,
run tftp, it will output:
Usage: tftp [OPTION]... HOST [PORT]
Transfer a file from/to tftp server
Options:
        -l FILE Local FILE
        -r FILE Remote FILE
        -g      Get file
        -p      Put file
        -b SIZE Transfer blocks of SIZE octets
I try serveral times, I find:
tftp -r hello.o -g 192.169.1.99
#comment:
My embedded platform is 192.168.1.168
I have a Linux PC, ip is 192.168.1.99
In Linux PC, hello.o put in folder /tftpboot/