How to send a symbol request

I want to send a symbol request to the Elektron ETA service. From an example at https://github.com/Refinitiv/Real-Time-SDK/blob/master/Cpp-C/Eta/Applications/Examples/Consumer/rsslSymbolListHandler.c, my code looks like below

RsslRet encodeSymbolListRequest(RsslChannel* chnl, RsslBuffer* msgBuf, RsslInt32 streamId)
{
RsslRet ret = 0;
RsslRequestMsg msg = RSSL_INIT_REQUEST_MSG;
RsslEncodeIterator encodeIter;
RsslLoginResponseInfo* loginInfo = getLoginResponseInfo();
RsslSourceDirectoryResponseInfo* srcDirRespInfo = 0;

if (getSourceDirectoryResponseInfo(getServiceId(), &srcDirRespInfo) != RSSL_RET_SUCCESS)

	return RSSL_RET_FAILURE;



rsslClearEncodeIterator(&encodeIter);



msg.msgBase.msgClass = RSSL_MC_REQUEST;

msg.msgBase.streamId = streamId;

msg.msgBase.domainType = RSSL_DMT_SYMBOL_LIST;

msg.msgBase.containerType = RSSL_DT_NO_DATA;

if (snapshotRequest)

{

	msg.flags = RSSL_RQMF_HAS_QOS | RSSL_RQMF_HAS_PRIORITY;

}

else

{ 

	msg.flags = RSSL_RQMF_HAS_QOS | RSSL_RQMF_STREAMING | RSSL_RQMF_HAS_PRIORITY;

}

msg.priorityClass = 1;

msg.priorityCount = 1;



rsslCopyQos(&(msg.qos), &(srcDirRespInfo->ServiceGeneralInfo.QoS[0]));


/*specify msgKey members*/

msg.msgBase.msgKey.flags = RSSL_MKF_HAS_NAME_TYPE | RSSL_MKF_HAS_NAME | RSSL_MKF_HAS_SERVICE_ID;

msg.msgBase.msgKey.nameType = RDM_INSTRUMENT_NAME_TYPE_RIC;

msg.msgBase.msgKey.serviceId = (RsslUInt16)getServiceId();




msg.msgBase.msgKey.name.length = (RsslUInt32)strlen(symbolListName);

msg.msgBase.msgKey.name.data = symbolListName;

}

How do I set symbolListName? The service that I am using rejects an empty service name. I am intetrested in streaming ticker data from the Elektron ETA service.

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Accepted answers

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wasin.w V3

Hello @LongLe

The rsslSymbolListHandler.c code did set the Service Name and Symbol List name on the following lines:

 static RsslRet encodeSymbolListRequest(RsslChannel* chnl, RsslBuffer* msgBuf, RsslInt32 streamId) 

{

	RsslRet ret = 0;

	RsslRequestMsg msg = RSSL_INIT_REQUEST_MSG;

	...

	msg.msgBase.msgKey.serviceId = (RsslUInt16)getServiceId();

	...

	msg.msgBase.msgKey.name.length = (RsslUInt32)strlen(symbolListName);

	if(msg.msgBase.msgKey.name.length != 0)

	{

		msg.msgBase.msgKey.name.data = symbolListName;

	}

To let us help you, please give us the following information:

How did you run the ETA Consumer? What is the command that you have run /Consumer example application?
What is the SymbolList RIC that you are trying?

You can check how to run the ETA Consumer example application on the ReadMe.txt file. The command for running a SymbolList request should be:

/Consumer -uname <DACS Username> -h <IProvider/ADS Hostname or IP Address> -p <RSSL Port> -s <ServiceName> -sl <SymbolList Name>

I also suggest you try the EMA C++ API which is the Message-Level API built on top of the ETA C. It is simpler, easier, and more friendly API interfaces than the ETA API while provides a high-performance data distribution for most of developers.

LongLe

Hi @wasin.w V3

I took the example code and built an application to get ticker data from an actual Elektron server. The example code sets the field msg.msgBase.msgKey.name to NULL or to "_ETA_ITEM_LIST", but the actual Elektron server rejects my request for symbol list. The Elektron server's source directory shows that it supports the domain for symbol list, but it does not provide further info. The file ReadMe.txt says "the symbol list name is optional", but that does not work.

Should I provide the exchange name for the symbols that I am interested in? If yes, in what form (full text name or acronyms)?

Please let me know how to set the field msg.msgBase.msgKey.name.

I'll look into EMA C++ API, but does EMA provide better performance (lower latency) than ETA? Thanks.

Jirapongse

This parameter is optional because the example can be used with other parameters, such as -mp, -mbo, and -mbp.

To run the example with the -sl parameter, you need to know RICs that can provide symbol list data, such as 0#.FCHISET.

You can contact the content support team directly via LSEG Support and ask for symbol list RICs that can provide your required data.

Regarding ETA and EMA: EMA is designed for ease of use, so ETA generally delivers better performance. However, the actual performance also depends on the application’s coding and design.

wasin.w V3

Hello @LongLe

Please be informed that the ETA provides a better performance than the EMA API in the trade-off that an application needs to do everything by itself such as (read/write socket, send heartbeat message, manage connection and subscription, etc.).

It is depending on your requirements that willing to do the manual low-level things to get a better performance.

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