[Nimbus][WebSockets] Exceptions being thrown when Nimbus connected to Nethermind by websockets

[kamilchodola]

To reproduce simply create a Nethermind <-> Nimbus node where on nimbus webSockets will be enabled:
--web3-url=ws://execution:8551/

Start the node and at Nethermind logs at the very first RPC received from Nimbus you should get this exception:

2024-05-15 10:07:00.9452|ERROR|JsonRpc.JsonRpcProcessor|76|Error during parsing/validation. System.Text.Json.JsonReaderException: The input does not contain any JSON tokens. Expected the input to start with a valid JSON token, when isFinalBlock is true. LineNumber: 1 | BytePositionInLine: 0.
   at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
   at System.Text.Json.JsonDocument.TryParseValue(Utf8JsonReader& reader, JsonDocument& document, Boolean shouldThrow, Boolean useArrayPools)
   at Nethermind.JsonRpc.JsonRpcProcessor.TryParseJson(ReadOnlySequence`1& buffer, JsonDocument& jsonDocument) in /_/src/Nethermind/Nethermind.JsonRpc/JsonRpcProcessor.cs:line 369
   at Nethermind.JsonRpc.JsonRpcProcessor.ProcessAsync(PipeReader reader, JsonRpcContext context)+MoveNext() in /_/src/Nethermind/Nethermind.JsonRpc/JsonRpcProcessor.cs:line 157
2024-05-15 10:07:00.9452|DEBUG|JsonRpc.JsonRpcService|76|Sending error response, method: none, id: , errorType: -32700, message: Incorrect message, errorData:  

Looking at RPC Recorder output there is:

root@ba043f4868cb:/nethermind/logs# cat rpc.0.txt
{"jsonrpc":"2.0","id":1,"method":"eth_getBlockByHash","params":["0x44bca881b07a6a09f83b130798072441705d9a665c5ac8bdf2f39a3cdf3bee29",false]}
{  "response": {    "jsonrpc": "2.0",    "result": null,    "id": 1  },  "report": {    "method": "eth_getBlockByHash",    "handlingTimeMicroseconds": "0x14db",    "success": true  }}
{  "response": {    "jsonrpc": "2.0",    "error": {      "code": -32700,      "message": "Incorrect message"    },    "id": null  },  "report": {    "method": "# parsing error #",    "handlingTimeMicroseconds": "0x8453",    "success": false  }}
{"jsonrpc":"2.0","id":2,"method":"eth_chainId","params":[]}
{  "response": {    "jsonrpc": "2.0",    "result": "0x1",    "id": 2  },  "report": {    "method": "eth_chainId",    "handlingTimeMicroseconds": "0x17c",    "success": true  }}
{  "response": {    "jsonrpc": "2.0",    "error": {      "code": -32700,      "message": "Incorrect message"    },    "id": null  },  "report": {    "method": "# parsing error #",    "handlingTimeMicroseconds": "0x15c2",    "success": false  }}

Which shows that RPC works well but for every request two responses are being generated (one valid and one invalid).

Node works fine but producing a lot of exceptions.