Couldn't access Go Server with base url.. broken pipe

Question

I'm installing a modern GoCD (16.7) on an Ubuntu machine. openjdk-8 (jre and jdk). The agents (on localhost) fail to connect to the server:

[Sat Jul 30 05:58:47 UTC 2016] Starting Go Agent Bootstrapper with command:
  /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java
  -jar /usr/share/go-agent3/agent-bootstrapper.jar
  -serverUrl https://127.0.0.1:8154/go/
...
java.lang.Exception: Couldn't access Go Server with base url:
  https://127.0.0.1:8154/go/admin/agent-launcher.jar:
  java.net.SocketException: Broken pipe
  at com.thoughtworks.go.agent.launcher.ServerCall.invoke(ServerCall.java:78)

and

2016-07-30 06:00:48,790 [main     ] ERROR go.agent.launcher.ServerBinaryDownloader:118
   - Couldn't update admin/agent-launcher.jar. Sleeping for 1m.
   Error: java.lang.Exception: Couldn't access Go Server with base url:
   https://127.0.0.1:8154/go/admin/agent-launcher.jar:
   java.net.SocketException: Broken pipe

(I manually wrapped those lines for readability)

The server is actually accessible. For instance:

$ curl --silent --insecure https://127.0.0.1:8154/go/ | head -2
<!-- *************************GO-LICENSE-START******************************
 * Copyright 2014 ThoughtWorks, Inc.

Yes, I'm using --insecure, but gocd ships with a self-signed cert. It's standard practice. Some of the things I've seen said "oh, you are blocking your port" but this is to localhost.

Answer 1

Are your GOCD server and agent using identical versions of Java? We have found they must be the same because the certificates have to match. See chatter