Hi, i already fix the bug, so i think this is the real bug. i set a callback fuc to GAtMux, and add status member for echo channel, when i find the channel active, it will call back the fuc, fuc check all channel is active, if all channel is active, continue to send AT commands you want. At 2012-11-06 22:23:21,"吴江波" <wujiangbo_1987(a)163.com&gt; wrote: Hi Denis Kenzior, I find a bug about ofono, in src/ifx.c. The function setup_internal_mux. if we modem use Mux in ofono code, ofono will create six channel to send request. After we send AT commands, each mux channel should be active that through send a little data and receive. In setup_internal_mux function it only set 10 millisecond to do that, it manual think channel active while 10 millisecond. if the modem don't response channel active in 10 millisecond, the sending AT commands don't dispatch to right channel. if you are lucky, ofono will work well, but it don't guarantee. and also i have the problem. ofono don't work well, it be cause by channel havn't configure, ofono send AT comands. The GAtMux receive the response, but GAtMux don't know which channel the response should be dispatched. GAtMux will discard the right response, and the AT command will don't receive the response forever, it will case some request timeout, and ofono think it have some problem it don't work. any questions. then we open mux, ofono will create a new IOChannel, the previously device IOChannel should remove from main context, but ofono don't do that. why? static void setup_internal_mux(struct ofono_modem *modem) { .............. g_at_mux_start(data->mux); for (i = 0; i < NUM_DLC; i++) { GIOChannel *channel = g_at_mux_create_channel(data->mux); data->dlcs[i] = create_chat(channel, modem, dlc_prefixes[i]); if (data->dlcs[i] == NULL) { ofono_error("Failed to create channel"); goto error; } } /* wait for DLC creation to settle */ data->dlc_init_source = g_timeout_add(10, dlc_setup, modem); .................... } Best regards And Thanks! Jiangbo.wu