Added the attribute packed struct command{ unsigned char cmd; unsigned int param; }__attribute__((packed)); The sizeof(cmd) is 8 it was also 8 before attrib packed was added. thanks ---------- Forwarded message ---------- From: Chris Svendsen <csvendsen2143@gmail.com> Date: Mon, Mar 25, 2013 at 1:10 PM Subject: RTL_TCP Commands To: osmocom-sdr@lists.osmocom.org Sending commands to RTL_TCP What format do the commands need to be in order to change the frequency of RTL_TCP. I have tried the following and the frequency will change but no to the frequency that is expected for example: This code : char SET_FREQUENCY[] ={0x01}; string Freq = string(SET_FREQUENCY,1)+"500000000"; answer = send(sConnect,Freq.c_str(),11,0); Changes the freq to this: client accepted! set freq 892350512 ll+, now 1 ll+, now 2 Any help would be greatly appreciated as i have been stuck on this for days. Thanks