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DEPRECATED: mbed TLS Socket Sample application

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This example has been deprecated

Please use sockets example instead.

TLSSocket example for Mbed OS

This examples application demonstrates the usage of TLSSocket API. To understand how secure sockets work in Mbed OS, please refer to the Documentation section below.
NOTE: This example works only on devices having TRNG supported!

Selecting the network interface

This application is able to use any network inteface it finds. Please see the Mbed OS documentation for selecting the default network interface.

For example, building on Ethernet enabled boards, you do not do any configuration.

Building for WiFi boards, you need to provide SSID, password and security settings in mbed_app.json as instructed in the documentation. For example, like this:

    "target_overrides": {
        "*": {
            "platform.stdio-convert-newlines": true,
            "": "WIFI",
            "nsapi.default-wifi-security": "WPA_WPA2",
            "nsapi.default-wifi-ssid": "\"ssid\"",
            "nsapi.default-wifi-password": "\"password\""

Building for boards that have more that one network interface, you might need to override variable.

Configuring mbedtls

It might be necessary to configure the mbedtls library with appropriate macros in mbed_app.json file. Some boards (like UBLOX_EVK_ODIN_W2) will work fine without any additional configuration and some of them might require some minimal adjustment. For example K64F will require at least the following macro added:

    "macros": ["MBEDTLS_SHA1_C"],
    "target_overrides": {

See mbedtls configuration guidelines for more details.


mbed compile -t <toolchain> -m <target>

For example, building for K64F using GCC: mbed compile -t GCC_ARM -m K64F

Expected output

Note: The default serial port baud rate is 9600 bit/s (8N1).

TLSSocket Example.
Mbed OS version: 5.11.4

Connecting to network
Connecting to
[DBG ][TLSW]: mbedtls_ssl_conf_ca_chain()
[INFO][TLSW]: Starting TLS handshake with
[DBG ][TLSW]: mbedtls_ssl_setup()
[INFO][TLSW]: TLS connection to established
[DBG ][TLSW]: Server certificate:
    cert. version     : 3
    serial number     : 0C:41:8C:DF:D9:3E:0D:A0:FC:7F:46:90:C1:64:A0:F2
    issuer name       : C=US, ST=CA, L=San Francisco, O=CloudFlare, Inc., CN=CloudFlare Inc ECC CA-2
    subject name      : C=US, ST=CA, L=San Francisco, O=Cloudflare, Inc.,
    issued  on        : 2020-01-30 00:00:00
    expires on        : 2020-10-09 12:00:00
    signed using      : ECDSA with SHA256
    EC key size       : 256 bits
    basic constraints : CA=false
    subject alt name  :
        dNSName :
        dNSName : *
        dNSName :
    key usage         : Digital Signature
    ext key usage     : TLS Web Server Authentication, TLS Web Client Authentication
    certificate policies : ???, ???

[INFO][TLSW]: Certificate verification passed
[DBG ][TLSW]: send 56
HTTP/1.1 200 OK
Date: Wed, 19 Feb 2020 11:06:02 GMT
Content-Type: text/html; charset=utf-8
Transfer-Encoding: chunked
Connection: close
Set-Cookie: __cfduid=da3c9233e724ec7c8b091ceac83d117c91582110361; expires=Fri, 20-Mar-20 11:06:01 GMT; path=/;; HttpOnly; SameSite=Lax
CF-Cache-Status: DYNAMIC
Expect-CT: max-age=604800, report-uri=""
Alt-Svc: h3-25=":443"; ma=86400, h3-24=":443"; ma=86400, h3-23=":443"; ma=86400
Server: cloudflare
CF-RAY: 5677c4e25b74fe34-HEL

...'s HTML code

[INFO][TLSW]: Closing TLS
[DBG ][TLSW]: mbedtls_ssl_conf_ca_chain()


For more information refer to following sections on the Mbed OS documentation:

License and contributions

The software is provided under Apache-2.0 license. Contributions to this project are accepted under the same license. Please see for more info.

This project contains code from other projects. The original license text is included in those source files. They must comply with our license guide.