Get timeout and rexmut from a r/w request in tftp protocol in c

Question

I'm trying to implement a tftp server. I've got a stucture :

typedef struct {
    u_int16_t opcode;
    char filename[MAXPATH_STRLEN + 1];
    char mode[MAXMODE_STRLEN + 1];
    char timeout[MAXMODE_STRLEN];
    char rexmut[MAXMODE_STRLEN];

} tftp_rwq_hdr;

where I accept a r/w request in tftp protol. When I'm using standart tftp to put a file, listening a request with this structure, I can get the opcode,filename and mode, but I can't get timeout neither rexmut.

So my question is what is the standart way to get the timeout and rexmut from a request like this.