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IoT Socket
Simple IP Socket (BSD like)
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IoT Socket
Simple IP Socket (BSD like)
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The IoT Socket pack provides a simple IP Socket API (BSD like) that implements the glue logic between IoT cloud connectors (IoT clients) and the underlying communication stack as shown on the picture below.
The IoT Socket implementation is maintained in a public GitHub repository. Its releases in CMSIS Pack format are available on CMSIS Packs page under MDK-Packs category and can be used in environments supporting the CMSIS-Pack concept.
Section Using IoT Socket describes how to integrate the IoT Socket components in a project and section Reference provides detailed documentation of available APIs.
IoT Socket implementation variants are available for the following network stacks:
With the IoT Socket Multiplexer functionality it is possible to retarget communication to a different socket interface at run-time (for example from a wireless to wired connection).
Typically, a user application does not call IoT Socket APIs directly, and relies on the IoT client interface that manages connectivity to the target service in the cloud.
An IoT client may already use IP sockets for communication and so can be easily ported to IoT Socket API. For cases when secure SSL/TLS sockets are required mbed TLS can be used. CMSIS-mbedTLS extends the mbedTLS library to use the IoT Socket API for network communication and so enables support for various IoT clients.
Following IoT client implementations work on top of the IoT Socket API either directly or via CMSIS-mbedTLS:
Keil Application Note 312 explains operation of these IoT clients.
keil.com/iot references example projects that implement wired and wireless connectivity to popular cloud services using extended IoT clients over IoT Socket interface. Figure below demonstrates the concept.
The table below lists the differences that IoT socket has comparing to BSD socket capabilities.
| Functionality | Support in IoT Socket | Support in BSD Socket |
|---|---|---|
| Address family | Only IPv4 and optionally IPv6, see IoT Socket Address Family. | Many other address families. |
| Socket type | Only STREAM and DGRAM, see IoT Socket Type. | Many other socket types. |
| Socket protocol | Only TCP and UDP, see IoT Socket Protocol. | Many other protocols. |
| Socket options | Only reduced set, see IoT Socket Options. | Many other socket options. |
| Address representation | Uses pointer to array of bytes, 4-bytes for IPv4, 16-bytes for IPv6, length is supplied with "ip_len" parameter. Port number is specified in host byte order Little Endian (LE). | Uses structure "sockaddr" that contains address family, IP address and port number. IP address and port number are specified in network byte order Big Endian (BE). |
| Errors | Returns error code as specified in IoT Socket Return Codes. | Returns -1 and sets the global "errno" on failure. |
| Host name resolving | Function iotSocketGetHostByName retrieves IPv4 or IPv6 address, requested address family is specified in "af" parameter. | Function "gethostbyname" retrieves only IPv4 addresses. The API function "getaddrinfo" is used to retrieve IPv4 or IPv6 addresses. |
| Read/write ability check1 | Uses receive functions called with parameter len=0. The function returns 0 if the socket is readable or writeable, otherwise the error code. There is no "select" function available. | Uses "select" function with a 0-timeout to check if the socket is readable or writeable. |
| Address conversion | APIs have no address conversion functions between ASCII (dot format) and network format. | Supports address conversion between ASCII and network format: "inet_addr", "inet_aton", "inet_ntoa", "inet_pton", "inet_ntop" |
1 Readable/writeable socket would not block on a send/receive call.
IoT Socket is provided under Apache 2.0 license.