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1. const net = require('net');

2. net.connect({port: 9999})

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1. events.js:170

2. throw er; // Unhandled 'error' event

3. ^

4.

5. Error: connect ECONNREFUSED 127.0.0.1:9999

6. at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1088:14)

7. Emitted 'error' event at:

8. at emitErrorNT (internal/streams/destroy.js:91:8)

9. at emitErrorAndCloseNT (internal/streams/destroy.js:59:3)

10. at processTicksAndRejections (internal/process/task_queues.js:81:17)

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1. const req = new TCPConnectWrap();

2. req.oncomplete = afterConnect;

3. req.address = address;

4. req.port = port;

5. req.localAddress = localAddress;

6. req.localPort = localPort;

7. // 开始三次握手建立连接

8. err = self._handle.connect(req, address, port);

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1. err = req_wrap->Dispatch(uv_tcp_connect,

2. &wrap->handle_,

3. reinterpret_cast<const sockaddr*>(&addr),

4. AfterConnect);

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1. do {

2. errno = 0;

3. // 非阻塞调用

4. r = connect(uv__stream_fd(handle), addr, addrlen);

5. } while (r == -1 && errno == EINTR);

6. // 连接错误，判断错误码

7. if (r == -1 && errno != 0) {

8. // 还在连接中，不是错误，等待连接完成，事件变成可读

9. if (errno == EINPROGRESS)

10. ; /* not an error */

11. else if (errno == ECONNREFUSED)

12. // 连接被拒绝

13. handle->delayed_error = UV__ERR(ECONNREFUSED);

14. else

15. return UV__ERR(errno);

16. }

17. uv__req_init(handle->loop, req, UV_CONNECT);

18. req->cb = cb;

19. req->handle = (uv_stream_t*) handle;

20. QUEUE_INIT(&req->queue);

21. // 挂载到handle，等待可写事件

22. handle->connect_req = req;

23. uv__io_start(handle->loop, &handle->io_watcher, POLLOUT);

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1. getsockopt(uv__stream_fd(stream),

2. SOL_SOCKET,

3. SO_ERROR,

4. &error,

5. &errorsize);

6. error = UV__ERR(error);

7. if (req->cb)

8. req->cb(req, error);

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1. Local<Value> argv[5] = {

2. Integer::New(env->isolate(), status),

3. wrap->object(),

4. req_wrap->object(),

5. Boolean::New(env->isolate(), readable),

6. Boolean::New(env->isolate(), writable)

7. };

8.

9. req_wrap->MakeCallback(env->oncomplete_string(), arraysize(argv), argv);

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1. const ex = exceptionWithHostPort(status,

2. 'connect',

3. req.address,

4. req.port,

5. details);

6. if (details) {

7. ex.localAddress = req.localAddress;

8. ex.localPort = req.localPort;

9. }

10. // 销毁socket

11. self.destroy(ex);

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1. function uvExceptionWithHostPort(err, syscall, address, port) {

2. const [ code, uvmsg ] = uvErrmapGet(err) || uvUnmappedError;

3. const message = `${syscall} $[code]: ${uvmsg}`;

4. let details = '';

5.

6. if (port && port > 0) {

7. details = ` ${address}:${port}`;

8. } else if (address) {

9. details = ` ${address}`;

10. }

11. const tmpLimit = Error.stackTraceLimit;

12. Error.stackTraceLimit = 0;

13. const ex = new Error(`${message}${details}`);

14. Error.stackTraceLimit = tmpLimit;

15. ex.code = code;

16. ex.errno = err;

17. ex.syscall = syscall;

18. ex.address = address;

19. if (port) {

20. ex.port = port;

21. }

22. // 获取调用栈信息但不包括当前调用的函数uvExceptionWithHostPort，注入stack字段到ex中

23. Error.captureStackTrace(ex, excludedStackFn || uvExceptionWithHostPort);

24. return ex;

25. }

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1. function uvErrmapGet(name) {

2. uvBinding = lazyUv();

3. if (!uvBinding.errmap) {

4. uvBinding.errmap = uvBinding.getErrorMap();

5. }

6. return uvBinding.errmap.get(name);

7. }

8.

9. function lazyUv() {

10. if (!uvBinding) {

11. uvBinding = internalBinding('uv');

12. }

13. return uvBinding;

14. }

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1. void GetErrMap(const FunctionCallbackInfo<Value>& args) {

2. Environment* env = Environment::GetCurrent(args);

3. Isolate* isolate = env->isolate();

4. Local<Context> context = env->context();

5.

6. Local<Map> err_map = Map::New(isolate);

7. // 从per_process::uv_errors_map中获取错误信息

8. size_t errors_len = arraysize(per_process::uv_errors_map);

9. // 赋值

10. for (size_t i = 0; i < errors_len; ++i) {

11. // map的键是 uv_errors_map每个元素中的value，值是name和message

12. const auto& error = per_process::uv_errors_map[i];

13. Local<Value> arr[] = {OneByteString(isolate, error.name),

14. OneByteString(isolate, error.message)};

15. if (err_map

16. ->Set(context,

17. Integer::New(isolate, error.value),

18. Array::New(isolate, arr, arraysize(arr)))

19. .IsEmpty()) {

20. return;

21. }

22. }

23.

24. args.GetReturnValue().Set(err_map);

25. }

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1. struct UVError {

2. int value;

3. const char* name;

4. const char* message;

5. };

6.

7. static const struct UVError uv_errors_map[] = {

8. #define V(name, message) {UV_##name, #name, message},

9. UV_ERRNO_MAP(V)

10. #undef V

11. };

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1. {UV_E2BIG, "E2BIG", "argument list too long"},

2. {UV_EACCES, "EACCES", "permission denied"},

3. {UV_EADDRINUSE, "EADDRINUSE", "address already in use"},

4. ……

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1. {

2. // 键是一个数字，由Libuv定义，其实是封装了操作系统的定义

3. UV_ECONNREFUSED: ["ECONNREFUSED", "connection refused"],

4. UV_ECONNRESET: ["ECONNRESET", "connection reset by peer"]

5. ...

6. }

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1. static void tcp_reset(struct sock *sk)

2. {

3. switch (sk->sk_state) {

4. case TCP_SYN_SENT:

5. sk->sk_err = ECONNREFUSED;

6. break;

7. // ...

8. }

9.

10. }