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Iothub_sdk_options.md

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IoTHub C SDK Options

This document describes how to set the options available in the c sdk.

Setting an Option

Setting an option in the c-sdk is dependant on which api set you are using:

// Convience Layer
IOTHUB_CLIENT_RESULT IoTHubClient_SetOption(IOTHUB_CLIENT_HANDLE iotHubClientHandle, const char* optionName, const void* value)

// Single Thread API
IOTHUB_CLIENT_RESULT IoTHubClient_LL_SetOption(IOTHUB_CLIENT_LL_HANDLE iotHubClientHandle, const char* optionName, const void* value)

An example of using a set option:

bool trace_on = true;
IoTHubClient_SetOption(sdk_handle, OPTION_LOG_TRACE, &trace_on);

HTTP_PROXY_OPTIONS http_proxy;
memset(&http_proxy, 0, sizeof(HTTP_PROXY_OPTIONS));
http_proxy.host_address = PROXY_ADDRESS;
http_proxy.port = PROXY_PORT;
DPS_LL_SetOption(handle, OPTION_HTTP_PROXY, &http_proxy);

Available Options

IoThub_Client

Option Name Option Define Value Type Description
"messageTimeout" OPTION_MESSAGE_TIMEOUT tickcounter_ms_t* (DEPRECATED) Timeout used for message on the message queue
"blob_upload_timeout_secs" OPTION_BLOB_UPLOAD_TIMEOUT_SECS size_t* Timeout in seconds of blob uploads
"product_info" OPTION_PRODUCT_INFO const char* User defined Product identifier sent to the IoThub service
"TrustedCerts" OPTION_TRUSTED_CERT const char* Azure Server certificate used to validate TLS connection to iothub

Standard Transport

Option Name Option Define Value Type Description
"logtrace" OPTION_LOG_TRACE bool* value Turn on and off log tracing for the transport
"sas_token_lifetime" OPTION_SAS_TOKEN_LIFETIME size_t* value Length of time in seconds used for lifetime of sas token.
"x509certificate" OPTION_X509_CERT const char* Sets an RSA x509 certificate used for connection authentication
"x509privatekey" OPTION_X509_PRIVATE_KEY const char* Sets the private key for the RSA x509 certificate
"x509EccCertificate" OPTION_X509_ECC_CERT const char* Sets the ECC x509 certificate used for connection authentication
"x509EccAliasKey" OPTION_X509_ECC_KEY const char* Sets the private key for the ECC x509 certificate
"proxy_data" OPTION_HTTP_PROXY HTTP_PROXY_OPTIONS* Http proxy data object used for proxy connection to IoTHub
"tls_version" OPTION_TLS_VERSION int* TLS version to use for openssl, 10 for version 1.0, 11 for version 1.1, 12 for version 1.2

MQTT Transport

Option Name Option Define Value Type Description
"keepalive" OPTION_KEEP_ALIVE int* Length of time to send Keep Alives to service for D2C Messages
"auto_url_encode_decode" OPTION_AUTO_URL_ENCODE_DECODE bool* Turn on and off automatic URL Encoding and Decoding.

AMQP Transport

Option Name Option Define Value Type Description
"cbs_request_timeout" OPTION_CBS_REQUEST_TIMEOUT size_t* value Amount of seconds to wait for a cbs request to complete
"sas_token_refresh_time" OPTION_SAS_TOKEN_REFRESH_TIME size_t* value Frequency in seconds that the SAS token is refreshed
"event_send_timeout_secs" OPTION_EVENT_SEND_TIMEOUT_SECS size_t* value Amount of seconds to wait for telemetry message to complete
"c2d_keep_alive_freq_secs" OPTION_C2D_KEEP_ALIVE_FREQ_SECS size_t* value Informs service of maximum period the client waits for keep-alive message

HTTP Tansport

Option Name Option Define Value Type Description
"Batching" OPTION_BATCHING bool* value Turn on and off message batching
"MinimumPollingTime" OPTION_MIN_POLLING_TIME unsigned int* value Minimum time in seconds allowed between 2 consecutive GET issues to the service
"timeout" OPTION_HTTP_TIMEOUT long* value When using curl the amount of time before the request times out, defaults to 242 seconds.

Additional notes

Batching and IoTHub Client SDK

Batching is the ability of a protocol to send multiple messages in one payload, rather than one at a time. This can result in less overhead, especially when sending multiple, small messages. This SDK supports various levels of batching when using IoTHubClient_SendEventAsync / IoTHubClient_LL_SendEventAsync.

  • AMQP uses batching always.

  • HTTP can optionally enable batching, using the "Batching" option referenced above.

  • MQTT does not have a batching option.

None of the protocols has a windowing or Nagling concept; e.g. they do NOT wait a certain amount of time to attempt to queue up multiple messages to put into a single batch. Instead they just batch whatever is on the to-send queue. For customers using the lower-layer protocols (LL), they can force batching via

IoTHubClient_LL_SendEventAsync(msg1) IoTHubClient_LL_SendEventAsync(msg2) IoTHubClient_LL_DoWork()