DocID027745 Rev 1

19/31

AN4683

Demonstration package

31

Note:

The accept parameter specifies the TCP port to listen for connections. If not specified, the

default 4433 is used.

To start the client, it is recommended to run AT+S.TLSCERT2=clean,all to clean the Flash

memory, and then use these AT commands:

AT+S.SETTIME=<seconds>

AT+S.TLSCERT=f_ca,<size><CR><data>

AT+S.TLSCERT=f_cert,<size><CR><data>

AT+S.TLSCERT=f_key,<size><CR><data>

AT+S.TLSDOMAIN=f_domain,<server domain>

AT+S.SOCKON=<hostname>,<port>,s[,ind]

Note:

Seconds is the current time expressed in seconds since 1970-01-01: AT+S.SETTIME can

be done only once after module reset.

AT+S.TLSCERT=<f_ca/f_cert/f_key>,<size><CR><data> stores certificates or key files (in

PEM format) to Flash memory of the module. The first input parameter is used to indicate

when a root CA certificate (f_ca), a client certificate (f_cert) or key file (f_key) is passed to

the module. This command accepts data after the <CR> at the end of the command line.

The host is expected to supply <size> of data as last parameter of the command line. The

size values must be expressed in bytes.

AT+S.TLSDOMAIN=f_domain,<server domain> passes the server domain to the module

and stores the domain information to Flash memory. The server domain is a string of

characters that must match the name specified in the server certificate (Common Name or

others).

When using AT+S.TLSCERT and AT+S.TLSDOMAIN with f_ca, f_cert, f_key and f_domain,

the file information is stored to Flash memory: since Flash memory is non-volatile, any file

stored in Flash memory will remain intact even when switching off or resetting the module.

Thus, to remove file information from Flash you can use the command

AT+S.TLSCERT2=clean,<f_ca|f_cert|f_key|f_domain> to selectively remove a specific file,

or AT+S.TLSCERT2=clean,all to remove all files information from Flash ones.

Note that loading files to Flash memory is always preferred! Alternatively, you may use

AT+S.TLSCERT=<ca/cert/key>,<size><CR><data> and

AT+S.TLSDOMAIN=domain,<server domain> to load files to RAM, but note that (a) RAM is

volatile and in this case the loaded file information is lost after switch off or module reset; (b)

files stored in RAM have higher priority than Flash ones; (c) files upload to RAM is

deprecated in favor of Flash.

AT+S.SOCKON=<hostname>,<port>,s[,ind] opens a secure socket to server hostname on

port. The hostname is the IP address of the server, the port must correspond to the one

specified in OpenSSL server options, and the s parameter specifies a request for secure

socket. The parameter ind is optional and provides the indication (WIND:55, see below) that

some data has been received: if enabled, it is strongly suggested to immediately empty the

buffer when a pending data is received (see SOCKQ and SOCKR commands below).

When the TLS handshake is successful, the AT+S.SOCKON gives back the sock id: only

then is it possible to write data to and read from the secure socket using AT+S.SOCKW,

AT+S.SOCKQ and AT+S.SOCKR.

If the parameter ind was enabled in SOCKON, asynchronous indications of pending data

from the secure socket may arrive at any time and have the format:

<CR><LF>+WIND:55:Pending Data:<sock id>:ENC<CR><LF>