AN4683 datasheet(20/31 Pages) STMICROELECTRONICS

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Demonstration package

AN4683

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When WIND:55 indications occur, the pending data is still encrypted, thus the length of

decrypted data is not known in advance. The SOCKQ can be used to get the actual length

of the data decrypted by TLS library and already waiting for reading.

Up to 4 consecutive WIND:55 messages (w/o SOCKR) are guaranteed. To prevent data

loss, it is suggested to empty the buffer by using the AT+S.SOCKR command and to avoid

exceeding 4 indications.

AT+S.SOCKW=<sock id>,<len>

AT+S.SOCKQ=<sock id>

AT+S.SOCKR=<sock id>,<len>

Note:

When using a secure socket, the module can handle data packets up to 3 KB. This means

that the len parameter in AT+S.SOCKW and AT+S.SOCKR can be up to 3072 bytes.

Detailed description of AT commands is contained in (see [2] in References).

3.4

Example 2: TLS Client with one-way authentication

This second example implements a TLS connection supporting one-way authentication. The

server and CA use RSA-2048 authentication.

Before running the example, the SPWF01Sxxx (client) must be connected to the Wi-Fi LAN

as illustrated in Section 3.2 and OpenSSL must be installed on the PC (acting as server).

For testing purposes, OpenSSL-1.0.1i has been used as TLS Server. Documentation and

installation instructions are available on the OpenSSL website (see [12] in References).

The IP addresses of the client and server are automatically assigned by the network router.

To start the server, open a command prompt into the folder Project/Examples/Example2 and

run this line:

openssl s_server -cert server_cert.pem -key server_key.pem -accept <port>

Note:

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

the default 4433 is used.

To start the client, it's 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.TLSDOMAIN=f_domain,<server domain>

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

Note:

Seconds is the current time expressed in seconds since 1970-Jan-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 to

the module. In case of one-way authentication, only the CA certificate (f_ca) must be

loaded, the data must be in PEM format. 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

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