JMeter TCP采样器读取异常求助：响应码500，读取字节数为0

Hey there, let’s dig into this tricky TCP sampler issue you’re hitting. That ReadException: Error reading from server, bytes read: 0 error is a real headache, especially after you’ve already tried adjusting EOL settings, timeouts, connection reuse, and connection closure options. Let’s walk through some additional troubleshooting steps that might get you past this:

1. Validate Your Request Payload Exactness #

TCP services often have strict requirements for message formatting—think mandatory length prefixes, checksum values, or specific character encodings (ASCII vs. UTF-8 vs. binary). A tiny mismatch here can cause the server to drop the connection without a response.

• Use a tool like Wireshark to capture traffic from both JMeter and a working client (like telnet or nc commands) when sending requests to the server. Compare the raw byte streams to spot differences.
• If your request uses binary data, use JMeter’s __hexStringToBytes() function to ensure the payload is sent correctly as bytes, not converted to a string which could corrupt the data.
• Double-check if the server expects a fixed-length message—if so, pad your request with the necessary bytes to match the required length.

2. Test Manual Connection to the Server #

Before blaming JMeter, confirm the server actually responds to requests from a basic client:

• Run nc <your-server-host> <your-server-port> in a terminal, then manually type/paste your request payload and hit enter. If you get no response here, the issue is likely on the server side (e.g., incorrect port, firewall rules, service not running, or request validation failure).
• If the manual test works, it means JMeter’s configuration is still missing something—revisit your connection settings (like whether "Reuse connection" aligns with the server’s expectations) and payload formatting.

3. Tweak Timeout Settings More Aggressively #

Sometimes even small adjustments to timeouts can make a difference:

• Increase both Connection Timeout and Response Timeout in the TCP sampler to 10000ms (10 seconds) or higher. The server might be taking longer to process the request than JMeter’s default timeout allows.
• Ensure you’re using milliseconds as the unit (JMeter’s default for these fields) to avoid accidental under-setting.

4. Switch to the Binary TCP Sampler #

If you’re using the standard TCP Sampler, try the Binary TCP Sampler instead (available in most recent JMeter versions):

• This sampler is designed specifically for binary payloads, avoiding string encoding issues that can corrupt your request. It’s often more reliable for non-text-based TCP services.

5. Enable Debug Logging for Detailed Insights #

Your current log only shows basic test startup info—enable debug logging to see exactly what’s happening with the TCP connection:

• Open jmeter.properties (in your JMeter bin directory) and set:

  log_level.org.apache.jmeter.protocol.tcp=DEBUG
  

• Restart JMeter and run your test again. The debug log will show details like:
  • Exact bytes sent to the server
  • Connection establishment/closure events
  • Any low-level errors that aren’t showing up in the sampler’s response message

Error & Log Context for Reference #

Reported Error:
Response Code: 500, Response Message: org.apache.jmeter.protocol.tcp.sampler.ReadException: Error reading from server, bytes read: 0

JMeter Log Snippet:

2018-04-24 12:09:09,740 INFO o.a.j.e.StandardJMeterEngine: Running the test!
2018-04-24 12:09:09,741 INFO o.a.j.s.SampleEvent: List of sample...

内容的提问来源于stack exchange，提问作者Kiran Maroju