{"record":{"id":"3380b2d3cf0df5cb","repo":"fatedier/frp","slug":"get-natholerespmsg-error-v","errorCode":null,"errorMessage":"get natHoleRespMsg error: %v","messagePattern":"get natHoleRespMsg error: (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"pkg/nathole/nathole.go","lineNumber":103,"sourceCode":"\n// PreCheck is used to check if the proxy is ready for penetration.\n// Call this function before calling Prepare to avoid unnecessary preparation work.\nfunc PreCheck(\n\tctx context.Context, transporter transport.MessageTransporter,\n\tproxyName string, timeout time.Duration,\n) error {\n\ttimeoutCtx, cancel := context.WithTimeout(ctx, timeout)\n\tdefer cancel()\n\n\tvar natHoleRespMsg *msg.NatHoleResp\n\ttransactionID := NewTransactionID()\n\tm, err := transporter.Do(timeoutCtx, &msg.NatHoleVisitor{\n\t\tTransactionID: transactionID,\n\t\tProxyName:     proxyName,\n\t\tPreCheck:      true,\n\t}, transactionID, msg.TypeNameNatHoleResp)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"get natHoleRespMsg error: %v\", err)\n\t}\n\tmm, ok := m.(*msg.NatHoleResp)\n\tif !ok {\n\t\treturn fmt.Errorf(\"get natHoleRespMsg error: invalid message type\")\n\t}\n\tnatHoleRespMsg = mm\n\n\tif natHoleRespMsg.Error != \"\" {\n\t\treturn fmt.Errorf(\"%s\", natHoleRespMsg.Error)\n\t}\n\treturn nil\n}\n\n// Prepare is used to do some preparation work before penetration.\nfunc Prepare(stunServers []string, opts PrepareOptions) (*PrepareResult, error) {\n\t// discover for Nat type\n\taddrs, localAddr, err := Discover(stunServers, \"\")\n\tif err != nil {","sourceCodeStart":85,"sourceCodeEnd":121,"githubUrl":"https://github.com/fatedier/frp/blob/6c8a8d0a97d03b44e9528d30b30c70cb9d61b405/pkg/nathole/nathole.go#L85-L121","documentation":"Returned by nathole.PreCheck (pkg/nathole/nathole.go) when the underlying transporter.Do round-trip fails while sending a NatHoleVisitor{PreCheck:true} and waiting for the matching NatHoleResp. This is the transport-level failure (send error, timeout, connection closed) — distinct from a server-side rejection, which arrives as a successful response carrying an Error string.","triggerScenarios":"nathole.PreCheck(ctx, transporter, proxyName, timeout) where transporter.Do errors: the control/UDP connection to frps is broken, the timeout context fires before the response arrives, or the message transport was already closed.","commonSituations":"frps unreachable or restarted mid-precheck; timeout passed to PreCheck too short for a slow link; visitor's connection to the nathole controller dropped (UDP); network flapping between visitor and server.","solutions":["Inspect the wrapped error — a context deadline means raise the timeout or fix latency; a connection error means re-establish the transport first","Retry PreCheck after reconnecting the transport","Verify frps is up and the nathole controller port is reachable from the visitor","Only call Prepare after PreCheck succeeds to avoid wasted discovery work"],"exampleFix":"// before\nerr := nathole.PreCheck(ctx, tp, proxyName, 500*time.Millisecond)\n\n// after\nerr := nathole.PreCheck(ctx, tp, proxyName, 3*time.Second)\nif err != nil {\n    // reconnect transport and retry once before giving up\n}","handlingStrategy":"retry","validationCode":null,"typeGuard":null,"tryCatchPattern":"if err := nathole.PreCheck(ctx, tp, proxyName, 3*time.Second); err != nil {\n    if errors.Is(err, context.DeadlineExceeded) || strings.Contains(err.Error(), \"get natHoleRespMsg error\") {\n        // reconnect transport and retry once before surfacing to the user\n    }\n}","preventionTips":["Call PreCheck with a generous timeout on slow links","Ensure the transport to frps is healthy before prechecking","Always PreCheck before Prepare to avoid wasted STUN work"],"tags":["go","frp","nathole","network","timeout"],"backgroundTag":null,"analyzedSha":"6c8a8d0a97d03b44e9528d30b30c70cb9d61b405","analyzedAt":"2026-08-15T06:53:27.215Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}