This is the documentation for the latest (main) development branch of Zephyr. If you are looking for the documentation of previous releases, use the drop-down list at the bottom of the left panel and select the desired version.

Large HTTP download


The sockets/big_http_download sample application for Zephyr implements a simple HTTP GET client using a BSD Sockets compatible API. Unlike the HTTP GET using plain sockets sample application, it downloads a file of several megabytes in size, and verifies its integrity using hashing. It also performs download repeatedly, tracking the total number of bytes transferred. Thus, it can serve as a “load testing” application for the Zephyr IP stack.

The source code for this sample application can be found at: samples/net/sockets/big_http_download.


  • Networking with the host system

  • or, a board with hardware networking

  • NAT/routing should be set up to allow connections to the Internet

  • DNS server should be available on the host to resolve domain names

Building and Running

Build the Zephyr version of the application like this:

west build -b <board_to_use> samples/net/sockets/big_http_download

After the sample starts, it issues an HTTP GET request for This site was selected as providing files of variety of sizes, together with various hashes for them, to ease external selection and verification. The particular file selected is 6.7MB in size, so it can show how reliably Zephyr streams non-trivial amounts of data, while still taking a reasonable amount of time to complete. While the file is downloaded, its hash is computed (SHA-256 is used in the source code), and an error message is printed if it differs from the reference value, as specified in the source code. After a short pause, the process repeats (in an infinite loop), while the total counter of the bytes received is kept. Thus the application can be used to test transfers of much larger amounts of traffic over a longer time.

You can edit the source code to issue a request to any other site on the Internet (or on the local network, in which case no NAT/routing setup is needed).


If you are doing extensive testing with this sample, please reference a file on a local server or a special-purpose testing server of your own on the Internet. Using files on is not recommended for large-scale testing.

Enabling TLS support

Enable TLS support in the sample by building the project with the overlay-tls.conf overlay file enabled, for example, using these commands:

west build -b qemu_x86 samples/net/sockets/big_http_download -- -DCONF_FILE="prj.conf overlay-tls.conf"

An alternative way is to specify -DEXTRA_CONF_FILE=overlay-tls.conf when running west build or cmake.

The TLS version of this sample downloads a file from (6.6MB). The certificates used by the sample are in the sample’s src directory and are used to access the default website configured in the sample for TLS communication ( and possible redirects. To access a different web page over TLS, you’ll need to provide a different certificate to authenticate to that server.

Note, that TLS support in the sample depends on non-posix, TLS socket functionality. Therefore, it is only possible to run TLS in this sample on Zephyr.

Running application on POSIX Host

The same application source code can be built for a POSIX system, e.g. Linux.

To build:

$ make -f

To run:

$ ./big_http_download

The behavior of the application is the same as the Zephyr version.