v2rayN Core Startup Errors: Fix JSON Syntax and Port Conflicts

1. Review startup output: distinguish a core exit from a connection failure

v2rayN is the management interface; Xray is the core that handles connections. An open window doesn’t mean the core is listening on a local port. Conversely, a web page timing out doesn’t prove the core failed to start: the remote host may be unreachable, routing rules may not work as expected, or an app may not use the system proxy. Any of these can happen while the core is running normally.

Find the latest startup record in the information or log area of the v2rayN main window. The entry name may vary by version, so use the log access point in your current interface. Note the startup time, core name, executable path, config path, and the first error before the process exits. Don’t save only the final “startup failed” message; it usually describes the outcome, not the cause.

2. Test the actual config: check JSON first, then Xray fields

The settings saved in the v2rayN interface aren’t the same as the runtime config passed to the core. Use startup output to find the actual config path, then make a copy for troubleshooting. Direct edits to an automatically generated runtime file may be overwritten when you switch nodes or restart. Once you find the cause, fix it in the custom config, routing rules, or relevant settings that generated the file.

1. Stop the failed startup attempt, save the error output, and back up the relevant current config.
2. Find the file specified in the startup arguments. Don’t guess from its filename or mistake subscription text for the core’s JSON config.
3. Test the copy with the same Xray executable that v2rayN actually runs.
4. Change one thing at a time and test again. Fix the next error only after the previous one is gone.

The steps below assume you’re in a test directory containing xray.exe and the copy to test, config.json. This filename is for the example only; v2rayN doesn’t always use this path. The first command checks the executable version. The second tests the config without starting the full proxy service.

.\xray.exe version
.\xray.exe run -test -config ".\config.json"
$LASTEXITCODE

A successful config test means only that the core passed this stage of config checks; it doesn’t guarantee that a port can be bound or a remote host reached. If your core doesn’t recognize the command-line arguments, check that executable’s help output to confirm the correct syntax. Don’t keep trying with an executable from an unknown source.

A config can be structurally valid but still have semantic errors. Xray field names are case-sensitive: outboundTag is not outboundtag. Routing rules must also reference an outbound tag that’s actually defined. Some unknown fields may be ignored rather than causing startup to fail, so “no syntax errors” doesn’t prove that field names are correct.

{
  "type": "field",
  "domain": ["full:example.com"],
  "outboundTag": "proxy"
}

3. Check for local port conflicts: identify the process behind a listening port

If the config test passes but startup still exits while binding a listener, check the port. Find listen, port, and the protocol in the runtime config’s inbounds. A TUN interface is not the same as a regular local proxy listener. The example below assumes TCP port 10808 is in conflict; it isn’t a default for every installation.

Get-NetTCPConnection -State Listen -LocalPort 10808 -ErrorAction SilentlyContinue |
  Select-Object LocalAddress, LocalPort, OwningProcess

# Replace 1234 below with the OwningProcess from the previous output
Get-Process -Id 1234 |
  Select-Object Id, ProcessName, Path

If the process path is blank, check the PID in Task Manager. If needed, use a terminal with appropriate permissions. Don’t terminate a process until you’ve confirmed what it is. The port may be in use by another v2rayN instance, a leftover Xray process, or an entirely different local service.

netsh interface ipv4 show excludedportrange protocol=tcp
netsh interface ipv6 show excludedportrange protocol=tcp

If you need to change ports, look for the local listening port setting in v2rayN under “Settings” → “Parameter Settings.” The group name may vary between versions; use the generated config as the source of truth. Before changing the test port from 10808 to 10818, for example, confirm that 10818 is free and not restricted. After restarting the core, update any manually configured browser proxy, terminal proxy variables, and other clients as well.

4. Check core files: paths, architecture, and dependencies

If even the config test won’t run, focus on the program files. First confirm that the full path in the log exists, then check whether the program can print its version directly. The v2rayN interface directory isn’t necessarily the core directory. Running a same-named program from another folder may test a different copy of Xray.

• Path: In PowerShell, use the call operator & with a full path that contains spaces. Put the config file path in quotes too.
• Architecture: Make sure the selected package matches your operating system and processor. If the program won’t load, check architecture and system compatibility first.
• File status: Check your security software’s quarantine and block logs to see which file was actually blocked. Don’t disable all security protection.
• Resources: Rules using geosite: or geoip: categories depend on the corresponding resource files. Troubleshoot missing resources separately from JSON syntax errors.

If the log shows failed to open file or The system cannot find the file specified., check the specific filename in the following lines. A missing executable, config file, or rule resource each calls for a different fix. For relative paths, also check the startup working directory and resource lookup location; confirming that “the file exists somewhere” isn’t enough.

5. Retest in order: verify a local request after the config passes

Finish troubleshooting with a repeatable end-to-end check, not just a change in the interface status. Keep the node, routing, and proxy mode unchanged; test only the part you just fixed. The request examples below apply only if port 10808 is confirmed to provide an HTTP proxy or a compatible mixed inbound. If the inbound supports SOCKS only, use the matching proxy protocol.

# HTTP proxy or mixed inbound with HTTP support
curl.exe --proxy http://127.0.0.1:10808 --connect-timeout 10 --max-time 20 https://example.com/

# SOCKS-only inbound: let the proxy resolve the destination hostname
curl.exe --proxy socks5h://127.0.0.1:10808 --connect-timeout 10 --max-time 20 https://example.com/

1. Config: Confirm that the core test passes with the same runtime config, then save the corrected source settings.
2. Startup: Confirm that the core stays running and the original error no longer appears in the startup log.
3. Listener: Check the target port again and confirm that the owning process is the core you just started.
4. Request: Send one request through the specified proxy endpoint, then compare its destination and outbound entry in the logs.

The 10-second connection timeout and 20-second total limit in the example are test settings, not performance benchmarks. If a local “connection refused” error occurs, recheck the listening endpoint. If the proxy connection succeeds but the remote request times out, continue checking the node, DNS, and routing. One successful request doesn’t prove every route works as intended, but it does distinguish a core startup failure from a problem with a specific connection.

6. Common questions: subscriptions, config tests, and reinstalling