Java.io.IOException: Error writing to server异常；我测试500个并发时，系统没有问题；可当我把线程数加到800时，就出现错误了，在“查看结果树”中，打开出错的请求，看到如下异常：
java.io.IOException: Error writing to server
at sun.reflect.GeneratedConstructorAccessor24.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at sun.Net.www.protocol.http.HttpURLConnection$6.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.net.www.protocol.http.HttpURLConnection.getChainedException(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at org.apache.jmeter.protocol.http.sampler.HTTPSampler.readResponse(HTTPSampler.java:222)
at org.apache.jmeter.protocol.http.sampler.HTTPSampler.sample(HTTPSampler.java:433)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java:658)
at org.apache.jmeter.protocol.http.sampler.HTTPSamplerBase.sample(HTTPSamplerBase.java:647)
at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:247)
at java.lang.Thread.run(Unknown Source)
Caused by: java.io.IOException: Error writing to server
at sun.net.www.protocol.http.HttpURLConnection.writeRequests(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.writeRequests(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getHeaderField(Unknown Source)
at java.net.URLConnection.getContentEncoding(Unknown Source)
at org.apache.jmeter.protocol.http.sampler.HTTPSampler.readResponse(HTTPSampler.java:213)
... 5 more
解决方法：
修改了/bin/jmeter.bat文件：找到这2行
set HEAP=-Xms256m -Xmx256m
set NEW=-XX:NewSize=128m -XX:MaxNewSize=128m
改为：
set HEAP=-Xms256m -Xmx1024m
set NEW=-XX:NewSize=128m -XX:MaxNewSize=512m
然后就不在报错了。