从gin的启动开始看socket是如何在服务器中创建的：
gin -> net/http -> net -> internal/syscall -> syscall -> runtime
通过上面的调用流程，可以看出，http是对net的封装，方便开发者调用，实际创建Socket的还是net库，底层已经是到了go的syscall和runtime库了。
最终调用的还是操作系统提供的socket接口。这就是socket创建的流程。
具体流程涉及的文件以及代码：
router.go
r := gin.New()
r.Run(address) // host:port
github.com\gin-gonic\gin@v1.7.7\gin.go
err = http.ListenAndServe(address, engine)
Go\src\net\http\server.go
// Go net/http包
return server.ListenAndServe()
ln, err := net.Listen("tcp", addr) // http也是对net的封装
if err != nil {
return err
}
Go\src\net\dial.go
return lc.Listen(context.Background(), network, address)
l, err = sl.listenTCP(ctx, la)
Go\src\net\tcpsock_posix.go
fd, err := internetSocket(ctx, sl.network, laddr, nil, syscall.SOCK_STREAM, 0, "listen", sl.ListenConfig.Control)
Go\src\net\ipsock_posix.go
return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr, ctrlFn) // 出现socket函数了
Go\src\net\sock_posix.go
// socket returns a network file descriptor that is ready for
// asynchronous I/O using the network poller.
s, err := sysSocket(family, sotype, proto)
Go\src\net\sock_windows.go
s, err := wsaSocketFunc(int32(family), int32(sotype), int32(proto),nil, 0, windows.WSA_FLAG_OVERLAPPED|windows.WSA_FLAG_NO_HANDLE_INHERIT)
Go\src\net\hook_windows.go
wsaSocketFunc func(int32, int32, int32, *syscall.WSAProtocolInfo, uint32, uint32) (syscall.Handle, error) = windows.WSASocket // windows.WSASocket就是返回的socket
Go\src\internal\syscall\windows\zsyscall_windows.go
// 可以看到文件已经跳转到internal文件夹下的系统相关调用目录
func WSASocket(af int32, typ int32, protocol int32, protoInfo *WSAProtocolInfo, group uint32, flags uint32) (handle Handle, err error) {
r0, _, e1 := syscall.Syscall6(procWSASocketW.Addr(), 6, uintptr(af), uintptr(typ), uintptr(protocol), uintptr(unsafe.Pointer(protoInfo)), uintptr(group), uintptr(flags))
handle = Handle(r0)
if handle == InvalidHandle {
err = errnoErr(e1)
}
return
}
=== r0 start ===
Go\src\syscall\dll_windows.go
// 可以看到文件已经跳转到syscall系统调用目录，dll_windows名称也可看出该文件底层调用的是windos系统提供的接口。
// Implemented in ../runtime/syscall_windows.go.
// 注释中是说继承于../runtime/syscall_windows.go文件中的Syscall6，这个写法比较特殊，是go1.14刚出的，go:linkname，有兴趣的可以继续深入这个写法，这里不做赘述。
func Syscall6(trap, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
Go\src\runtime\syscall_windows.go
//go:linkname syscall_Syscall6 syscall.Syscall6
//go:nosplit
//go:cgo_unsafe_args
func syscall_Syscall6(fn, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr) {
lockOSThread()
defer unlockOSThread()
c := &getg().m.syscall
c.fn = fn
c.n = nargs
c.args = uintptr(noescape(unsafe.Pointer(&a1)))
cgocall(asmstdcallAddr, unsafe.Pointer(c))
return c.r1, c.r2, c.err
}
=== r0 end ===
