Configure openthread for mqtt - tcp connection times out?

Question

Hi, I am in need of some guidance. The overall goal is to set up MQTT/TLS communication from end devices in a thread network, via a border router to the AWS cloud. I have my nrf52840DK up and running in the thread network, it has got a IPv6 address from the border router (a KiBRA KTBRN1) via DHCPv6 and I am able to ping in both directions. 
 My problem is that the TCP connection is not setup correctly and I suspect that I have missed something in the configuration. 
 
 on my dev pc: 
 ubuntu:~$ ifconfig | grep inet inet 192.168.1.49 netmask 255.255.255.0 broadcast 192.168.1.255 inet6 fd47:d3c:923f:0:20c:29ff:fe88:7ce1 prefixlen 64 scopeid 0x0<global> 
 ubuntu:~$ ping -6 -c2 fd7e:b200:ced:0:0:0:a2e:24 PING fd7e:b200:ced:0:0:0:a2e:24 (fd7e:b200:ced::a2e:24) 56 data bytes 64 bytes from fd7e:b200:ced::a2e:24: icmp_seq=1 ttl=63 time=42.5 ms 64 bytes from fd7e:b200:ced::a2e:24: icmp_seq=2 ttl=63 time=39.0 ms 
 --- fd7e:b200:ced:0:0:0:a2e:24 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1002ms rtt min/avg/max/mdev = 39.054/40.793/42.532/1.739 ms 
 ubuntu:~$ nc -l 1234 
 
 Then on the thread device: 
 uart:~$ ot ipaddr fd7e:b200:ced:0:0:0:a2e:24 fdd9:20b7:f073:0:0:ff:fe00:1800 fdd9:20b7:f073:0:597f:71e6:d5f5:3775 fe80:0:0:0:b849:ed15:1dba:12ab Done 
 uart:~$ ot ping 64:ff9b::c0a8:131 Done 16 bytes from 64:ff9b:0:0:0:0:c0a8:131: icmp_seq=1 hlim=63 time=57ms 
 uart:~$ ot ping fd47:d3c:923f:0:20c:29ff:fe88:7ce1 Done 16 bytes from fd47:d3c:923f:0:20c:29ff:fe88:7ce1: icmp_seq=2 hlim=63 time=58ms uart:~$ 
 uart:~$ net ping 64:ff9b::c0a8:131 PING 64:ff9b::c0a8:131 8 bytes from 64:ff9b::c0a8:131 to fd7e:b200:ced::a2e:24: icmp_seq=0 ttl=63 rssi=0 time=88.50 ms 8 bytes from 64:ff9b::c0a8:131 to fd7e:b200:ced::a2e:24: icmp_seq=1 ttl=63 rssi=0 time=87.65 ms 8 bytes from 64:ff9b::c0a8:131 to fd7e:b200:ced::a2e:24: icmp_seq=2 ttl=63 rssi=0 time=87.40 ms 
 uart:~$ net ping fd47:d3c:923f:0:20c:29ff:fe88:7ce1 PING fd47:d3c:923f:0:20c:29ff:fe88:7ce1 8 bytes from fd47:d3c:923f:0:20c:29ff:fe88:7ce1 to fd7e:b200:ced::a2e:24: icmp_seq=0 ttl=63 rssi=0 time=88.17 ms 8 bytes from fd47:d3c:923f:0:20c:29ff:fe88:7ce1 to fd7e:b200:ced::a2e:24: icmp_seq=1 ttl=63 rssi=0 time=114.07 ms 8 bytes from fd47:d3c:923f:0:20c:29ff:fe88:7ce1 to fd7e:b200:ced::a2e:24: icmp_seq=2 ttl=63 rssi=0 time=88.01 ms 
 So far it looks good, but when I try to open a tcp connection it fails. 
 uart:~$ net tcp connect fd47:d3c:923f:0:20c:29ff:fe88:7ce1 1234 Connecting from [fd7e:b200:ced::a2e:24]:0 to [fd47:d3c:923f:0:20c:29ff:fe88:7ce1]:1234 uart:~$ 
 Here is the debuglog: 
 D: (shell_uart): conn: 0x2001b780, ref_count: 1
D: (shell_uart): conn: 0x2001b780
D: (shell_uart): Context 0x2000c3e0 binding to TCP [fd7e:b200:ced::a2e:24]:35896 iface 0x200008e4
D: (shell_uart): context: 0x2000c3e0, local: fd7e:b200:ced::a2e:24, remote: fd47:d3c:923f:0:20c:29ff:fe88:7ce1
D: (shell_uart): conn: 0x2001b780 src: fd7e:b200:ced::a2e:24, dst: fd47:d3c:923f:0:20c:29ff:fe88:7ce1
D: (shell_uart): [0x2000c8d8/6/2/0x7f] remote fd47:d3c:923f:0:20c:29ff:fe88:7ce1/1234 
D: (shell_uart): local fd7e:b200:ced::a2e:24/35896 cb 0x19ea9 ud 0x2000c3e0
D: (shell_uart): [LISTEN Seq=3781784924 Ack=0]
D: (shell_uart): On iface 0x200008e4 size 20
D: (shell_uart): HDRs length estimation 68
D: (shell_uart): Data allocation maximum size 88 (requested 20)
D: (shell_uart): TDATA (?) [0] frag 0x20019d58 ref 1 (tcp_out_ext():776)
D: (shell_uart): pkt 0x20018ad0 data 0x20019fc0 length 40
D: (shell_uart): pkt 0x20018ad0 skip 40
D: (shell_uart): pkt 0x20018ad0 data 0x20019fe8 length 20
D: (shell_uart): pkt 0x20018ad0 skip 20
D: (shell_uart): pkt 0x20018ad0 data 0x20019fc0 length 40
D: (shell_uart): pkt 0x20018ad0 skip 40
D: (shell_uart): pkt 0x20018ad0 skip 8
D: (shell_uart): pkt 0x20018ad0 skip 32
D: (shell_uart): pkt 0x20018ad0 data 0x20019fe8 length 20
D: (shell_uart): pkt 0x20018ad0 skip 20
D: (shell_uart): pkt 0x20018ad0 skip 40
D: (shell_uart): pkt 0x20018ad0 skip 40
D: (shell_uart): SYN Seq=3781784924 Len=0
D: (shell_uart): pkt 0x20018ad0 skip 40
D: (shell_uart): pkt 0x20018ad0 skip 40
D: (shell_uart): SYN Seq=3781784924 Len=0 
D: (shell_uart): pkt 0x20018ad0 skip 40
D: (shell_uart): On iface 0x200008e4 size 60
D: (shell_uart): Data allocation maximum size 60 (requested 60)
D: (shell_uart): TDATA (?) [0] frag 0x20019d70 ref 1 (net_pkt_clone():1765)
D: (shell_uart): pkt 0x20018a80 skip 40
D: (shell_uart): Cloned 0x20018ad0 to 0x20018a80
D: (shell_uart): pkt 0x20018a80 skip 40
D: (shell_uart): pkt 0x20018a80 skip 40
D: (shell_uart): SYN Seq=3781784924 Len=0
D: (shell_uart): TX [12] pkt 0x20018a80 ref 2 (tcp_send():284)
D: (tx_q[0]): Processing (pkt 0x20018a80, prio 1) network packet iface 0x200008e4/1
D: (openthread): TX [12] pkt 0x20018a80 ref 1 frags 0x20019d70 (openthread_handle_frame_to_send():362)
D: (shell_uart): TX [12] pkt 0x20018a80 ref 0 frags 0x20019d70 (tcp_send():325)
D: (shell_uart): TDATA (?) [0] frag 0x20019d70 ref 0 frags (nil) (tcp_send():325)
D: (shell_uartD: (ot_radio_workq): On iface 0x200008e4 size 3
D: (ot_radio_workq): Data allocation maximum size 3 (requested 3)
D: (ot_radio_workq): TDATA (?) [0] frag 0x20019d88 ref 1 (handle_ack():384)
D: (ot_radio_workq): pkt 0x20018a30 data 0x2001088d length 3
D: (ot_radio_workq): pkt 0x20018a30 data 0x2000cbe4 length 3
D: (ot_radio_workq): TX [11] pkt 0x20018a30 ref 0 frags 0x20019d88 (handle_ack():412)
D: (ot_radio_workq): TDATA (?) [0] frag 0x20019d88 ref 0 frags (nil) (handle_ack():412)
D: (ot_radio_workq): TDATA (?) [0] frag 0x20019d88 ref 0 (net_pkt_unref_debug():586)
): TDATA (?) [0] frag 0x20019d70 ref 0 (net_pkt_unref_debug():586)
D: (shell_uart): LISTEN->SYN_SENT
D: (shell_uart): conn: 0x2001b780, ref_count=1
D: (shell_uart): Connection handler 0x2000c8d8 removed
D: (shell_uart): context: 0x2000c3e0, conn: (nil)
D: (shell_uart): Context 0x2000c3e0 released
D: (shell_uart): TX [13] pkt 0x20018ad0 ref 0 frags 0x20019d58 (tcp_send_queue_flush():336)
D: (shell_uart): TDATA (?) [0] frag 0x20019d58 ref 0 frags (nil) (tcp_send_queue_flush():336)
D: (shell_uart): TDATA (?) [0] frag 0x20019d58 ref 0 (net_pkt_unref_debug():586)
D: (shell_uart): TX [14] pkt 0x20018b20 ref 0 frags (nil) (tcp_conn_unref():389)
D: (shell_uart): RX [9] pkt 0x20018670 ref 0 frags (nil) (tcp_conn_unref():392)
D: (shell_uart): conn: 0x2001b780, ret=-116

My configuration 
 CONFIG_GPIO=y
CONFIG_FPU=y
CONFIG_MAIN_STACK_SIZE=2048
CONFIG_NCS_SAMPLES_DEFAULTS=y
CONFIG_LOG_DEFAULT_LEVEL=4
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=4096
CONFIG_MBEDTLS_HEAP_SIZE=10240
CONFIG_OPENTHREAD_RADIO_WORKQUEUE_STACK_SIZE=1024
# CONFIG_MBEDTLS_CIPHER_MODE_CBC is not set
# CONFIG_MBEDTLS_CIPHER_MODE_CTR is not set
# CONFIG_MBEDTLS_CHACHA20_C is not set
# CONFIG_MBEDTLS_POLY1305_C is not set
# CONFIG_MBEDTLS_DHM_C is not set
# CONFIG_MBEDTLS_RSA_C is not set
# CONFIG_MBEDTLS_SHA1_C is not set
# CONFIG_MBEDTLS_SHA512_C is not set
CONFIG_OPENTHREAD_LIBRARY_1_1=y
CONFIG_OPENTHREAD_NORDIC_LIBRARY_MASTER=y
CONFIG_SOC_SERIES_NRF52X=y
CONFIG_SOC_NRF52840_QIAA=y
CONFIG_ARM_MPU=y
CONFIG_NUM_METAIRQ_PRIORITIES=1
CONFIG_CONSOLE=y
CONFIG_RTT_CONSOLE=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_UART_LINE_CTRL=y
CONFIG_ENTROPY_NRF5_THR_THRESHOLD=4
CONFIG_ENTROPY_NRF5_ISR_THRESHOLD=12
CONFIG_USB=y
CONFIG_NEWLIB_LIBC=y
# CONFIG_STDOUT_CONSOLE is not set
CONFIG_STACK_SENTINEL=y
CONFIG_NETWORKING=y
CONFIG_NET_L2_OPENTHREAD=y
CONFIG_OPENTHREAD_MANUAL_START=y
CONFIG_OPENTHREAD_FULL_LOGS=y
CONFIG_OPENTHREAD_JOINER_AUTOSTART=y
CONFIG_OPENTHREAD_JOINER_PSKD="1LABAB"
CONFIG_OPENTHREAD_DEBUG=y
CONFIG_OPENTHREAD_L2_DEBUG=y
CONFIG_OPENTHREAD_L2_LOG_LEVEL_INF=y
# CONFIG_OPENTHREAD_MBEDTLS is not set
CONFIG_NET_IF_MCAST_IPV6_ADDR_COUNT=4
# CONFIG_NET_IPV6_MLD is not set
# CONFIG_NET_IPV6_NBR_CACHE is not set
CONFIG_NET_SHELL=y
CONFIG_NET_TCP=y
CONFIG_NET_PKT_RX_COUNT=10
CONFIG_NET_PKT_TX_COUNT=16
CONFIG_NET_BUF_DATA_SIZE=256
CONFIG_NET_STATISTICS=y
CONFIG_NET_LOG=y
CONFIG_NET_CONN_LOG_LEVEL_DBG=y
CONFIG_MQTT_LIB=y
CONFIG_NET_SOCKETS_POSIX_NAMES=y
CONFIG_NET_SOCKETS_POLL_MAX=4
CONFIG_NET_CONNECTION_MANAGER=y
CONFIG_UART_SHELL_ON_DEV_NAME="CDC_ACM_0"
CONFIG_USB_DEVICE_VID=0x1915
CONFIG_USB_DEVICE_PID=0x520F
CONFIG_USB_DEVICE_MANUFACTURER="Unitware"
CONFIG_USB_DEVICE_PRODUCT="Zigbee NCP"
CONFIG_USB_CDC_ACM=y
CONFIG_DEBUG_OPTIMIZATIONS=y

Unitware · Accepted Answer

Hi Charlie, thanks for looking at this. I agree that TCP is not the best choice but it would enable us to get direct contact with AWS IoT over MQTT with no middlemen. The openthread API does not have TCP, but it is possible to open a ipv6 socket and transmit that way. according to this document at least it is allowed: https://portal.threadgroup.org/DesktopModules/Inventures_Document/FileDownload.aspx?ContentID=633 page 13: UDP and TCP 
 Thread Devices use UDP (User Datagram Protocol) as defined in [RFC 768] for messaging between devices for mesh establishment and maintenance. Thread Networks also support TCP (or any other IPv6-based transport protocol) for application layer communication. 
 And reading the spec it is mandatory to support UDP, and optional to support TCP. Anyway, If anybody know of a good scalable solution to connect threaddevices to AWS I'd be interested to hear about it.

Configure openthread for mqtt - tcp connection times out?

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