# FreeRTOS TCP/IP pdFREERTOS\_ERRNO\_ENOMEM (Nucleo-F767Zi) **URL:** \ **Category:** Libraries\ **Created:** [March 11, 2020, 1:47pm UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219 "2020-03-11T13:47:28Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Stud\_David](https://avatars.discourse-cdn.com/v4/letter/s/977dab/32.png) [@Stud\_David](https://forums.freertos.org/u/Stud_David)\ **Post date:** [March 11, 2020, 1:47pm UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219/1 "2020-03-11T13:47:28Z")
Hi, I’m currently working on getting the FreeRTOS TCP/IP stack running on the Nucleo-F767Zi. The goal is to communicate with my PC over an ethernet cable. It is currently running so far that I can connect successfully with my Pc. If I want to send or receive a message I get the error code pdFREERTOS\_ERRNO\_ENOMEM back from the commands FreeRTOS\_recv and FreeRTOS\_send. Even if I want to send or receive a simple 1. I’m a bit at a loss as to how to fix this error. In the API References there is the following sentence : **If there was not enough memory for the socket to be able to create either an Rx or Tx stream then -pdFREERTOS\_ERRNO\_ENOMEM is returned.** But unfortunately I can’t do anything with it. What does this error tell me and how can I fix it. I set the StackDepth to 400, ipconfigTCP\_MSS is set to 1460 and ipconfigNETWORK\_MTU to 1526. For further information I use the BufferAllocation\_2 as advised and in the FreeRTOSConfig.h I set #define configSUPPORT\_DYNAMIC\_ALLOCATION to 1. ---
**Author:** ![rtel](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/rtel/32/31_2.png) [@rtel](https://forums.freertos.org/u/rtel)\ **Post date:** [March 11, 2020, 2:32pm UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219/2 "2020-03-11T14:32:56Z")
Where is pdFREERTOS\_ERRNO\_ENOMEM getting set? If I look in FreeRTOS\_send() I see it calls prvTCPSendCheck(), and inside prvTCPSendCheck() pdFREERTOS\_ERRNO\_ENOMEM gets set if either “pxSocket-\>u.xTCP.bits.bMallocError != pdFALSE\_UNSIGNED” or “pxSocket-\>u.xTCP.txStream == NULL”. That would seem to be indicative of a malloc() failure. Which [heap allocation scheme](https://www.freertos.org/a00111.html) are you using? What is configTOTAL\_HEAP\_SIZE set to? Do you have a [malloc failed hook](https://www.freertos.org/a00016.html) defined? ---
**Author:** ![Stud\_David](https://avatars.discourse-cdn.com/v4/letter/s/977dab/32.png) [@Stud\_David](https://forums.freertos.org/u/Stud_David)\ **Post date:** [March 11, 2020, 2:47pm UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219/3 "2020-03-11T14:47:36Z")
Thank you for responding so quickly. pdFREERTOS\_ERRNO\_ENOMEM is set at send and receive with the if condition pxSocket-\>u.xTCP.bits.bMallocError != pdFALSE\_UNSIGNED. I use the heap\_4 allocation scheme and my whole heap is set as #define configTOTAL\_HEAP\_SIZE ((size\_t)15360) I have not defined the malloc failed hook. ---
**Author:** ![rtel](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/rtel/32/31_2.png) [@rtel](https://forums.freertos.org/u/rtel)\ **Post date:** [March 11, 2020, 5:51pm UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219/4 "2020-03-11T17:51:24Z")
> [@Stud\_David](#): > > I have not defined the malloc failed hook. Recommend you do define this as it would give you quick insight to where you issue was as as far as I can see bMallocError can only get set here [https://github.com/FreeRTOS/FreeRTOS/blob/V10.3.1/FreeRTOS-Plus/Source/FreeRTOS-Plus-TCP/FreeRTOS\_Sockets.c#L2958](https://github.com/FreeRTOS/FreeRTOS/blob/V10.3.1/FreeRTOS-Plus/Source/FreeRTOS-Plus-TCP/FreeRTOS_Sockets.c#L2958) which would have triggered the malloc failed hook. So you have run out of heap, which means you either need to tune your system, [including the TCP stack](https://www.freertos.org/FreeRTOS-Plus/FreeRTOS_Plus_TCP/TCP_IP_Configuration_Examples.html), to use less memory or you need to increase the heap site. ---
**Author:** ![htibosch](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/htibosch/32/62_2.png) [@htibosch](https://forums.freertos.org/u/htibosch)\ **Post date:** [March 12, 2020, 5:42am UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219/5 "2020-03-12T05:42:49Z")
Here is a short overview of the usage of RAM in a mid-size MCU: | ipconfig item | Value | | | | --- | --- | --- | --- | | NETWORK\_MTU | 1500 | | | | TCP\_MSS | 1460 | | | | USE\_TCP | 1 | | | | USE\_TCP\_WIN | 1 | | | | TCP\_RX\_BUFFER\_LENGTH | 2920 | | | | TCP\_TX\_BUFFER\_LENGTH | 2920 | | | | USE\_DHCP | 0 | | | | | | | | | RAM that is always allocated (statically or on the heap): | | | | | ipconfig item | Value | PerUnit | Total | | NUM\_NETWORK\_BUFFER\_DESCRIPTORS | 8 | 1572 | 12576 | | TCP\_WIN\_SEG\_COUNT | 32 | 64 | 2048 | | EVENT\_QUEUE\_LENGTH | 25 | 8 | 200 | | IP\_TASK\_STACK\_SIZE\_WORDS | 512 | 4 | 2048 | | ARP\_CACHE\_ENTRIES | 6 | 12 | 72 | | DNS\_CACHE\_ENTRIES | 4 | 28 | 112 | | Total | | | 17056 | In the first column you see the `ipconfig` item, like e.g. `ipconfigNETWORK_MTU`. Beside the above, malloc will be used to allocate sockets and their TCP stream buffers. The length of the stream buffers depends on `ipconfigTCP_RX_BUFFER_LENGTH` and `ipconfigTCP_TX_BUFFER_LENGTH`, unless overridden by the socket options `FREERTOS_SO_RCVBUF` and `FREERTOS_SO_SNDBUF`. | Object | Size | | --- | --- | | UDP-Socket | 100 | | TCP-Socket | 432 | | TX-Buffer | 2920 | | RX-Buffer | 2920 | When a TCP socket is only used in one direction, it will only create a single stream buffer. Note that BufferAllocation\_1.c is used, which means that all network buffers are allocated statically (8 x1572 bytes). ---
**Author:** ![Stud\_David](https://avatars.discourse-cdn.com/v4/letter/s/977dab/32.png) [@Stud\_David](https://forums.freertos.org/u/Stud_David)\ **Post date:** [March 12, 2020, 9:34am UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219/6 "2020-03-12T09:34:08Z")
Many thanks for the listing. Since I have only used the LwIP STACK to establish ethernet connections and the standard heap size of : #define configTOTAL\_HEAP\_SIZE ((size\_t)15360) for this always sufficed, I did not think that the heap size could be too small. But because of its listing I soon realized that I had to increase my TOTAL\_HEAP\_SIZE. Thanks for the fast and helpful tips. ---
**Author:** ![htibosch](https://d3iykfbgfh8zhg.cloudfront.net/user_avatar/forums.freertos.org/htibosch/32/62_2.png) [@htibosch](https://forums.freertos.org/u/htibosch)\ **Post date:** [March 12, 2020, 10:09am UTC](https://forums.freertos.org/t/freertos-tcp-ip-pdfreertos-errno-enomem-nucleo-f767zi/9219/7 "2020-03-12T10:09:16Z")
The utility that created the above table is now available in a [PR #1828](https://github.com/aws/amazon-freertos/pull/1828) Beside increasing `configTOTAL_HEAP_SIZE` you can also decrease the memory usage, especially with these macros: ```auto NUM_NETWORK_BUFFER_DESCRIPTORS TCP_RX_BUFFER_LENGTH TCP_TX_BUFFER_LENGTH TCP_WIN_SEG_COUNT NETWORK_MTU ``` They are all described on [FreeRTOS.org](https://freertos.org)