Send multicast on esp8266?

Question

I'm working on esp8266, nonos sdk v 2.0.0_16_08_10, native c. I'm monitoring the network via wireshark.

I'm trying to send a multicast message over udp.

Receiving udp multicasts works. Sending udp unicasts works. Sending udp multicasts doesn't work.

In my udp send callback function, it is indicated that the message is sent, but I cant catch it via wireshark.

Multicast IP address: 224.0.1.187 Multicast port: 5683

Joining multicast group:

uint32_t mip = wifi_get_ip();
if(mip == 0){
    os_printf("ERROR MULTICAST JOIN mip==0\n");
    return;
}

ip_addr_t local, remote;
remote.addr = ocf_mgroup.ip.full;
local.addr = mip;

os_printf("multicast result = %d\n", espconn_igmp_join(&local, &remote));

Opening an UDP channel:

uint8_t ICACHE_FLASH_ATTR udp_open(uint8_t ch_no, uint8_t ch_id, uint32_t src_addr, uint16_t src_port, uint32_t dst_addr, uint16_t dst_port){
    //ALLOC MEM
    udp_conn[ch_no] = (struct espconn*) os_malloc(sizeof(struct espconn));
    udp_info[ch_no] = (esp_udp*) os_malloc(sizeof(esp_udp));

    //CHANNEL
    //ports
    udp_info[ch_no]->remote_port = dst_port;
    udp_info[ch_no]->local_port = src_port;
    //ips
    udp_info[ch_no]->remote_ip[0] = (dst_addr) & 0xff;
    udp_info[ch_no]->remote_ip[1] = (dst_addr >> 8) & 0xff;
    udp_info[ch_no]->remote_ip[2] = (dst_addr >> 16) & 0xff;
    udp_info[ch_no]->remote_ip[3] = (dst_addr >> 24) & 0xff;
    udp_info[ch_no]->local_ip[0] = (src_addr) & 0xff;
    udp_info[ch_no]->local_ip[1] = (src_addr >> 8) & 0xff;
    udp_info[ch_no]->local_ip[2] = (src_addr >> 16) & 0xff;
    udp_info[ch_no]->local_ip[3] = (src_addr >> 24) & 0xff;

    //connection
    udp_conn[ch_no]->type = ESPCONN_UDP;
    udp_conn[ch_no]->state = ESPCONN_NONE;
    udp_conn[ch_no]->proto.udp = udp_info[ch_no];
    udp_conn[ch_no]->link_cnt = ch_id;

    //HANDLERS
    espconn_regist_recvcb(udp_conn[ch_no], udp_receive_handler);
    //on send successfull
    espconn_regist_sentcb(udp_conn[ch_no], udp_send_handler);

    //CRAETE
    return espconn_create(udp_conn[ch_no]);
}

Sending a message to ip:port:

uint8_t ICACHE_FLASH_ATTR udp_send_cfg(uint8_t ch_no, uint8_t* data, uint16_t len, uint32_t dst_ip, uint16_t dst_port){
    udp_conn[ch_no]->proto.udp->remote_port = dst_port;

    udp_conn[ch_no]->proto.udp->remote_ip[0] = dst_ip & 0xFF;
    udp_conn[ch_no]->proto.udp->remote_ip[1] = (dst_ip >> 8) & 0xFF;
    udp_conn[ch_no]->proto.udp->remote_ip[2] = (dst_ip >> 16) & 0xFF;
    udp_conn[ch_no]->proto.udp->remote_ip[3] = (dst_ip >> 24) & 0xFF;

    return espconn_sent(udp_conn[ch_no], data, len);
}

See How to create a Minimal, Complete, and Verifiable example — Marcin Orlowski
Sorry, I though that this info is enough. Will add code soon. — Invader Zim
@InvaderZim, it helps if interested people with the necessary environment can simply copy and paste and run your code immediately and see what you are seeing. — sigjuice

Invader Zim Invader Zim · Accepted Answer · 2017-03-13T14:36:22

After extensive searching on the internet I found that soft-ap causes problem for multicast sending.

My code reads a configuration from flash, so I hard-coded that the ap configuration is NULL, and multicast is now being sent without a problem.

So, avoid the following functions:

wifi_set_opmode(STATIONAP_MODE)
wifi_set_opmode(SOFTAP_MODE)
wifi_softap_foo

I also found that soft-ap dhcp is specifically causing this problem, and sometimes I could send the multicast messages when it isn't turned on, but sometimes I couldn't.

The info I found is for Arduino, but seems to work for native c as well.

Send multicast on esp8266?

1 Answers