在Mule Anypoint Studio中使用代理连接第三方服务时遇“Connection Refused”错误

First, let's reference your HTTP request configuration for context:

<http:request-config name="HTTP_Request_Configuration" protocol="HTTPS" host="nww.neopost.sbs.nhs.uk" port="443" doc:name="HTTP Request Configuration" proxy-ref="Neopost_Global_Proxy_Configuration"> 
    <http:basic-authentication username="46234F3D-192C-4118-9A79-948F6C2053BB" password="F25038E0-53D6-4C06-8DFE-FF25FA3C82CD"/> 
    <tls:context> 
        <tls:trust-store path="C:/Java/jdk1.7.0_80/jre/lib/security/cacerts" password="changeit"/> 
    </tls:context> 
</http:request-config>

A "Connection Refused" error typically points to a TCP-level issue rather than an application or TLS problem. Let's walk through the most likely causes and how to test them:

1. Validate Your Global Proxy Configuration #

You're referencing Neopost_Global_Proxy_Configuration, but we don't have its details here. This is the first place to check:

• Double-check the proxy host and port in the global config—typos here are a super common culprit.
• If your proxy requires authentication, ensure you've added the correct credentials (username/password) in the proxy settings. Missing or invalid auth can sometimes present as a connection refusal.
• Confirm the proxy is configured to allow outbound connections to nww.neopost.sbs.nhs.uk on port 443. Some proxies restrict access to specific domains/ports.

2. Test Network Connectivity to the Proxy #

Before blaming Mule, rule out basic network issues from your Studio machine:

• Ping the proxy server to confirm it's reachable from your machine.
• Use telnet <proxy-host> <proxy-port> (or PowerShell's Test-NetConnection <proxy-host> -Port <proxy-port>) to verify the proxy port is open and accepting connections. If this fails, it's likely a firewall rule, network policy, or proxy downtime issue—check with your network team.
• Ensure your machine isn't using a conflicting proxy (e.g., system-wide proxy settings that don't match what's configured in Mule).

3. Confirm Target Service Accessibility via Proxy #

Even if the proxy is reachable, it might not be able to connect to the target service:

• Try accessing https://nww.neopost.sbs.nhs.uk directly in a browser using the same proxy settings as your Mule config. If the browser can't reach it, the issue is either with the target service or the proxy's ability to route to it.
• Ask your network team to verify that the proxy server has outbound access to nww.neopost.sbs.nhs.uk:443.

4. Check for TLS/Trust Store Edge Cases #

While "Connection Refused" is rarely a TLS issue, it's worth a quick check to rule out edge scenarios:

• Your config uses the JDK's default cacerts store. Ensure this store includes the root certificate for the target service (or that the proxy doesn't present an untrusted certificate). Note: A TLS certificate error usually throws a message like "unable to find valid certification path", but it's worth eliminating.
• If your proxy uses SSL inspection (man-in-the-middle), you'll need to add the proxy's CA certificate to your trust store.

5. Enable Debug Logs for More Context #

Turn on debug logging for the HTTP connector to get granular details about the connection failure:

1. Go to Run > Run Configurations > Mule Application > [Your App] > Logging
2. Set the log level for org.mule.module.http to DEBUG
3. Rerun your flow and check the logs. You might see clues like DNS resolution failures, proxy handshake issues, or explicit rejection messages from the proxy.

内容的提问来源于stack exchange，提问作者Videesh