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S7NetPlus / s7netplus

S7.NET+ -- A .NET library to connect to Siemens Step7 devices
MIT License
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ReadBytes Exception #384

Closed zzzdddyyy closed 3 years ago

zzzdddyyy commented 3 years ago

Function: I want read 1 byte from DB1,actually,DB1.0 is 1,0,0,0,0,0,0,0; The return value of this method should be [1],just 1 bytes,but somtimes i receive 15 bytes. code: byte[] rePLC_Status = MyPLC.ReadBytes(DataType.DataBlock, 1, 0, 1); Exception: S7.Net.PlcException:“Received 15 bytes: '32-03-00-00-00-07-00-02-00-01-00-00-05-01-FF', expected 19 bytes.”

mycroes commented 3 years ago

Hi @zzzdddyyy,

The 15 bytes received are part of the total message, which includes a header before the actual response. If it's only 15 bytes (instead of the expected 19). What's strange though is that the last byte should be the result code given by the PLC, and FF is the code for success. Is there any chance you're having concurrent access (multiple threads) to the PLC instance? That's currently not supported and does tend to lead to similar issues. #394 does address this issue though.

mycroes commented 3 years ago

Hi @zzzdddyyy, please retest this with v0.12.0.

zzzdddyyy commented 3 years ago

Thanks for your response.Yes,I used a timer loop to read DB variables.I will try to use the latest version

mycroes commented 3 years ago

Closing, feel free to reopen if the issue persists.

68jai90 commented 3 years ago

Hi everyone,

I am having the same issue when I want to read the data from S71500 Safety PLC. but the only difference is "S7.Net.PlcException:“Received 15 bytes: '32-02-00-00-00-00-00-00-00-00-81-04', expected 19 bytes.”".

I have used the same code to read from S71200 PLC, it was working fine. So I am not sure.

Can anyone assist me on this?

Jason-Jelks commented 3 years ago

When I ran into a possibly similar problem recently, I found that instantiating an instance with the overload PLC(string ip, TsapPair tsapPair) explicitly from my code reverts to S7-300, but if when I changed to the standard public Plc(CpuType cpu, string ip, int port, Int16 rack, Int16 slot), the issue resolved. If that doesn't help at all, it may help to understand what the structure (DB, Array, Input, Output...) you are attempting to read. We have S7-1212 and S7-1515F-2 PN Safety in house that we test our S7netPlus changes with.

mycroes commented 3 years ago

Hi everyone,

I am having the same issue when I want to read the data from S71500 Safety PLC. but the only difference is "S7.Net.PlcException:“Received 15 bytes: '32-02-00-00-00-00-00-00-00-00-81-04', expected 19 bytes.”".

I have used the same code to read from S71200 PLC, it was working fine. So I am not sure.

Can anyone assist me on this?

Probably missing get/put access, IIRC.

68jai90 commented 3 years ago

Hi everyone, I am having the same issue when I want to read the data from S71500 Safety PLC. but the only difference is "S7.Net.PlcException:“Received 15 bytes: '32-02-00-00-00-00-00-00-00-00-81-04', expected 19 bytes.”". I have used the same code to read from S71200 PLC, it was working fine. So I am not sure. Can anyone assist me on this?

Probably missing get/put access, IIRC.

Hi mycroes,

Yes, it was put/get access and also the access level. It was set accordingly, but it was not downloaded to the hardware. It was a silly mistake to overlook on that.

Thank you very much for taking time to reply guys.