| // Copyright 2010 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package net |
| |
| import ( |
| "context" |
| "internal/nettrace" |
| "syscall" |
| "time" |
| ) |
| |
| // defaultTCPKeepAlive is a default constant value for TCPKeepAlive times |
| // See golang.org/issue/31510 |
| const ( |
| defaultTCPKeepAlive = 15 * time.Second |
| ) |
| |
| // A Dialer contains options for connecting to an address. |
| // |
| // The zero value for each field is equivalent to dialing |
| // without that option. Dialing with the zero value of Dialer |
| // is therefore equivalent to just calling the Dial function. |
| // |
| // It is safe to call Dialer's methods concurrently. |
| type Dialer struct { |
| // Timeout is the maximum amount of time a dial will wait for |
| // a connect to complete. If Deadline is also set, it may fail |
| // earlier. |
| // |
| // The default is no timeout. |
| // |
| // When using TCP and dialing a host name with multiple IP |
| // addresses, the timeout may be divided between them. |
| // |
| // With or without a timeout, the operating system may impose |
| // its own earlier timeout. For instance, TCP timeouts are |
| // often around 3 minutes. |
| Timeout time.Duration |
| |
| // Deadline is the absolute point in time after which dials |
| // will fail. If Timeout is set, it may fail earlier. |
| // Zero means no deadline, or dependent on the operating system |
| // as with the Timeout option. |
| Deadline time.Time |
| |
| // LocalAddr is the local address to use when dialing an |
| // address. The address must be of a compatible type for the |
| // network being dialed. |
| // If nil, a local address is automatically chosen. |
| LocalAddr Addr |
| |
| // DualStack previously enabled RFC 6555 Fast Fallback |
| // support, also known as "Happy Eyeballs", in which IPv4 is |
| // tried soon if IPv6 appears to be misconfigured and |
| // hanging. |
| // |
| // Deprecated: Fast Fallback is enabled by default. To |
| // disable, set FallbackDelay to a negative value. |
| DualStack bool |
| |
| // FallbackDelay specifies the length of time to wait before |
| // spawning a RFC 6555 Fast Fallback connection. That is, this |
| // is the amount of time to wait for IPv6 to succeed before |
| // assuming that IPv6 is misconfigured and falling back to |
| // IPv4. |
| // |
| // If zero, a default delay of 300ms is used. |
| // A negative value disables Fast Fallback support. |
| FallbackDelay time.Duration |
| |
| // KeepAlive specifies the interval between keep-alive |
| // probes for an active network connection. |
| // If zero, keep-alive probes are sent with a default value |
| // (currently 15 seconds), if supported by the protocol and operating |
| // system. Network protocols or operating systems that do |
| // not support keep-alives ignore this field. |
| // If negative, keep-alive probes are disabled. |
| KeepAlive time.Duration |
| |
| // Resolver optionally specifies an alternate resolver to use. |
| Resolver *Resolver |
| |
| // Cancel is an optional channel whose closure indicates that |
| // the dial should be canceled. Not all types of dials support |
| // cancellation. |
| // |
| // Deprecated: Use DialContext instead. |
| Cancel <-chan struct{} |
| |
| // If Control is not nil, it is called after creating the network |
| // connection but before actually dialing. |
| // |
| // Network and address parameters passed to Control method are not |
| // necessarily the ones passed to Dial. For example, passing "tcp" to Dial |
| // will cause the Control function to be called with "tcp4" or "tcp6". |
| Control func(network, address string, c syscall.RawConn) error |
| } |
| |
| func (d *Dialer) dualStack() bool { return d.FallbackDelay >= 0 } |
| |
| func minNonzeroTime(a, b time.Time) time.Time { |
| if a.IsZero() { |
| return b |
| } |
| if b.IsZero() || a.Before(b) { |
| return a |
| } |
| return b |
| } |
| |
| // deadline returns the earliest of: |
| // - now+Timeout |
| // - d.Deadline |
| // - the context's deadline |
| // |
| // Or zero, if none of Timeout, Deadline, or context's deadline is set. |
| func (d *Dialer) deadline(ctx context.Context, now time.Time) (earliest time.Time) { |
| if d.Timeout != 0 { // including negative, for historical reasons |
| earliest = now.Add(d.Timeout) |
| } |
| if d, ok := ctx.Deadline(); ok { |
| earliest = minNonzeroTime(earliest, d) |
| } |
| return minNonzeroTime(earliest, d.Deadline) |
| } |
| |
| func (d *Dialer) resolver() *Resolver { |
| if d.Resolver != nil { |
| return d.Resolver |
| } |
| return DefaultResolver |
| } |
| |
| // partialDeadline returns the deadline to use for a single address, |
| // when multiple addresses are pending. |
| func partialDeadline(now, deadline time.Time, addrsRemaining int) (time.Time, error) { |
| if deadline.IsZero() { |
| return deadline, nil |
| } |
| timeRemaining := deadline.Sub(now) |
| if timeRemaining <= 0 { |
| return time.Time{}, errTimeout |
| } |
| // Tentatively allocate equal time to each remaining address. |
| timeout := timeRemaining / time.Duration(addrsRemaining) |
| // If the time per address is too short, steal from the end of the list. |
| const saneMinimum = 2 * time.Second |
| if timeout < saneMinimum { |
| if timeRemaining < saneMinimum { |
| timeout = timeRemaining |
| } else { |
| timeout = saneMinimum |
| } |
| } |
| return now.Add(timeout), nil |
| } |
| |
| func (d *Dialer) fallbackDelay() time.Duration { |
| if d.FallbackDelay > 0 { |
| return d.FallbackDelay |
| } else { |
| return 300 * time.Millisecond |
| } |
| } |
| |
| func parseNetwork(ctx context.Context, network string, needsProto bool) (afnet string, proto int, err error) { |
| i := last(network, ':') |
| if i < 0 { // no colon |
| switch network { |
| case "tcp", "tcp4", "tcp6": |
| case "udp", "udp4", "udp6": |
| case "ip", "ip4", "ip6": |
| if needsProto { |
| return "", 0, UnknownNetworkError(network) |
| } |
| case "unix", "unixgram", "unixpacket": |
| default: |
| return "", 0, UnknownNetworkError(network) |
| } |
| return network, 0, nil |
| } |
| afnet = network[:i] |
| switch afnet { |
| case "ip", "ip4", "ip6": |
| protostr := network[i+1:] |
| proto, i, ok := dtoi(protostr) |
| if !ok || i != len(protostr) { |
| proto, err = lookupProtocol(ctx, protostr) |
| if err != nil { |
| return "", 0, err |
| } |
| } |
| return afnet, proto, nil |
| } |
| return "", 0, UnknownNetworkError(network) |
| } |
| |
| // resolveAddrList resolves addr using hint and returns a list of |
| // addresses. The result contains at least one address when error is |
| // nil. |
| func (r *Resolver) resolveAddrList(ctx context.Context, op, network, addr string, hint Addr) (addrList, error) { |
| afnet, _, err := parseNetwork(ctx, network, true) |
| if err != nil { |
| return nil, err |
| } |
| if op == "dial" && addr == "" { |
| return nil, errMissingAddress |
| } |
| switch afnet { |
| case "unix", "unixgram", "unixpacket": |
| addr, err := ResolveUnixAddr(afnet, addr) |
| if err != nil { |
| return nil, err |
| } |
| if op == "dial" && hint != nil && addr.Network() != hint.Network() { |
| return nil, &AddrError{Err: "mismatched local address type", Addr: hint.String()} |
| } |
| return addrList{addr}, nil |
| } |
| addrs, err := r.internetAddrList(ctx, afnet, addr) |
| if err != nil || op != "dial" || hint == nil { |
| return addrs, err |
| } |
| var ( |
| tcp *TCPAddr |
| udp *UDPAddr |
| ip *IPAddr |
| wildcard bool |
| ) |
| switch hint := hint.(type) { |
| case *TCPAddr: |
| tcp = hint |
| wildcard = tcp.isWildcard() |
| case *UDPAddr: |
| udp = hint |
| wildcard = udp.isWildcard() |
| case *IPAddr: |
| ip = hint |
| wildcard = ip.isWildcard() |
| } |
| naddrs := addrs[:0] |
| for _, addr := range addrs { |
| if addr.Network() != hint.Network() { |
| return nil, &AddrError{Err: "mismatched local address type", Addr: hint.String()} |
| } |
| switch addr := addr.(type) { |
| case *TCPAddr: |
| if !wildcard && !addr.isWildcard() && !addr.IP.matchAddrFamily(tcp.IP) { |
| continue |
| } |
| naddrs = append(naddrs, addr) |
| case *UDPAddr: |
| if !wildcard && !addr.isWildcard() && !addr.IP.matchAddrFamily(udp.IP) { |
| continue |
| } |
| naddrs = append(naddrs, addr) |
| case *IPAddr: |
| if !wildcard && !addr.isWildcard() && !addr.IP.matchAddrFamily(ip.IP) { |
| continue |
| } |
| naddrs = append(naddrs, addr) |
| } |
| } |
| if len(naddrs) == 0 { |
| return nil, &AddrError{Err: errNoSuitableAddress.Error(), Addr: hint.String()} |
| } |
| return naddrs, nil |
| } |
| |
| // Dial connects to the address on the named network. |
| // |
| // Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only), |
| // "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4" |
| // (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and |
| // "unixpacket". |
| // |
| // For TCP and UDP networks, the address has the form "host:port". |
| // The host must be a literal IP address, or a host name that can be |
| // resolved to IP addresses. |
| // The port must be a literal port number or a service name. |
| // If the host is a literal IPv6 address it must be enclosed in square |
| // brackets, as in "[2001:db8::1]:80" or "[fe80::1%zone]:80". |
| // The zone specifies the scope of the literal IPv6 address as defined |
| // in RFC 4007. |
| // The functions JoinHostPort and SplitHostPort manipulate a pair of |
| // host and port in this form. |
| // When using TCP, and the host resolves to multiple IP addresses, |
| // Dial will try each IP address in order until one succeeds. |
| // |
| // Examples: |
| // |
| // Dial("tcp", "golang.org:http") |
| // Dial("tcp", "192.0.2.1:http") |
| // Dial("tcp", "198.51.100.1:80") |
| // Dial("udp", "[2001:db8::1]:domain") |
| // Dial("udp", "[fe80::1%lo0]:53") |
| // Dial("tcp", ":80") |
| // |
| // For IP networks, the network must be "ip", "ip4" or "ip6" followed |
| // by a colon and a literal protocol number or a protocol name, and |
| // the address has the form "host". The host must be a literal IP |
| // address or a literal IPv6 address with zone. |
| // It depends on each operating system how the operating system |
| // behaves with a non-well known protocol number such as "0" or "255". |
| // |
| // Examples: |
| // |
| // Dial("ip4:1", "192.0.2.1") |
| // Dial("ip6:ipv6-icmp", "2001:db8::1") |
| // Dial("ip6:58", "fe80::1%lo0") |
| // |
| // For TCP, UDP and IP networks, if the host is empty or a literal |
| // unspecified IP address, as in ":80", "0.0.0.0:80" or "[::]:80" for |
| // TCP and UDP, "", "0.0.0.0" or "::" for IP, the local system is |
| // assumed. |
| // |
| // For Unix networks, the address must be a file system path. |
| func Dial(network, address string) (Conn, error) { |
| var d Dialer |
| return d.Dial(network, address) |
| } |
| |
| // DialTimeout acts like Dial but takes a timeout. |
| // |
| // The timeout includes name resolution, if required. |
| // When using TCP, and the host in the address parameter resolves to |
| // multiple IP addresses, the timeout is spread over each consecutive |
| // dial, such that each is given an appropriate fraction of the time |
| // to connect. |
| // |
| // See func Dial for a description of the network and address |
| // parameters. |
| func DialTimeout(network, address string, timeout time.Duration) (Conn, error) { |
| d := Dialer{Timeout: timeout} |
| return d.Dial(network, address) |
| } |
| |
| // sysDialer contains a Dial's parameters and configuration. |
| type sysDialer struct { |
| Dialer |
| network, address string |
| } |
| |
| // Dial connects to the address on the named network. |
| // |
| // See func Dial for a description of the network and address |
| // parameters. |
| // |
| // Dial uses context.Background internally; to specify the context, use |
| // DialContext. |
| func (d *Dialer) Dial(network, address string) (Conn, error) { |
| return d.DialContext(context.Background(), network, address) |
| } |
| |
| // DialContext connects to the address on the named network using |
| // the provided context. |
| // |
| // The provided Context must be non-nil. If the context expires before |
| // the connection is complete, an error is returned. Once successfully |
| // connected, any expiration of the context will not affect the |
| // connection. |
| // |
| // When using TCP, and the host in the address parameter resolves to multiple |
| // network addresses, any dial timeout (from d.Timeout or ctx) is spread |
| // over each consecutive dial, such that each is given an appropriate |
| // fraction of the time to connect. |
| // For example, if a host has 4 IP addresses and the timeout is 1 minute, |
| // the connect to each single address will be given 15 seconds to complete |
| // before trying the next one. |
| // |
| // See func Dial for a description of the network and address |
| // parameters. |
| func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error) { |
| if ctx == nil { |
| panic("nil context") |
| } |
| deadline := d.deadline(ctx, time.Now()) |
| if !deadline.IsZero() { |
| if d, ok := ctx.Deadline(); !ok || deadline.Before(d) { |
| subCtx, cancel := context.WithDeadline(ctx, deadline) |
| defer cancel() |
| ctx = subCtx |
| } |
| } |
| if oldCancel := d.Cancel; oldCancel != nil { |
| subCtx, cancel := context.WithCancel(ctx) |
| defer cancel() |
| go func() { |
| select { |
| case <-oldCancel: |
| cancel() |
| case <-subCtx.Done(): |
| } |
| }() |
| ctx = subCtx |
| } |
| |
| // Shadow the nettrace (if any) during resolve so Connect events don't fire for DNS lookups. |
| resolveCtx := ctx |
| if trace, _ := ctx.Value(nettrace.TraceKey{}).(*nettrace.Trace); trace != nil { |
| shadow := *trace |
| shadow.ConnectStart = nil |
| shadow.ConnectDone = nil |
| resolveCtx = context.WithValue(resolveCtx, nettrace.TraceKey{}, &shadow) |
| } |
| |
| addrs, err := d.resolver().resolveAddrList(resolveCtx, "dial", network, address, d.LocalAddr) |
| if err != nil { |
| return nil, &OpError{Op: "dial", Net: network, Source: nil, Addr: nil, Err: err} |
| } |
| |
| sd := &sysDialer{ |
| Dialer: *d, |
| network: network, |
| address: address, |
| } |
| |
| var primaries, fallbacks addrList |
| if d.dualStack() && network == "tcp" { |
| primaries, fallbacks = addrs.partition(isIPv4) |
| } else { |
| primaries = addrs |
| } |
| |
| c, err := sd.dialParallel(ctx, primaries, fallbacks) |
| if err != nil { |
| return nil, err |
| } |
| |
| if tc, ok := c.(*TCPConn); ok && d.KeepAlive >= 0 { |
| setKeepAlive(tc.fd, true) |
| ka := d.KeepAlive |
| if d.KeepAlive == 0 { |
| ka = defaultTCPKeepAlive |
| } |
| setKeepAlivePeriod(tc.fd, ka) |
| testHookSetKeepAlive(ka) |
| } |
| return c, nil |
| } |
| |
| // dialParallel races two copies of dialSerial, giving the first a |
| // head start. It returns the first established connection and |
| // closes the others. Otherwise it returns an error from the first |
| // primary address. |
| func (sd *sysDialer) dialParallel(ctx context.Context, primaries, fallbacks addrList) (Conn, error) { |
| if len(fallbacks) == 0 { |
| return sd.dialSerial(ctx, primaries) |
| } |
| |
| returned := make(chan struct{}) |
| defer close(returned) |
| |
| type dialResult struct { |
| Conn |
| error |
| primary bool |
| done bool |
| } |
| results := make(chan dialResult) // unbuffered |
| |
| startRacer := func(ctx context.Context, primary bool) { |
| ras := primaries |
| if !primary { |
| ras = fallbacks |
| } |
| c, err := sd.dialSerial(ctx, ras) |
| select { |
| case results <- dialResult{Conn: c, error: err, primary: primary, done: true}: |
| case <-returned: |
| if c != nil { |
| c.Close() |
| } |
| } |
| } |
| |
| var primary, fallback dialResult |
| |
| // Start the main racer. |
| primaryCtx, primaryCancel := context.WithCancel(ctx) |
| defer primaryCancel() |
| go startRacer(primaryCtx, true) |
| |
| // Start the timer for the fallback racer. |
| fallbackTimer := time.NewTimer(sd.fallbackDelay()) |
| defer fallbackTimer.Stop() |
| |
| for { |
| select { |
| case <-fallbackTimer.C: |
| fallbackCtx, fallbackCancel := context.WithCancel(ctx) |
| defer fallbackCancel() |
| go startRacer(fallbackCtx, false) |
| |
| case res := <-results: |
| if res.error == nil { |
| return res.Conn, nil |
| } |
| if res.primary { |
| primary = res |
| } else { |
| fallback = res |
| } |
| if primary.done && fallback.done { |
| return nil, primary.error |
| } |
| if res.primary && fallbackTimer.Stop() { |
| // If we were able to stop the timer, that means it |
| // was running (hadn't yet started the fallback), but |
| // we just got an error on the primary path, so start |
| // the fallback immediately (in 0 nanoseconds). |
| fallbackTimer.Reset(0) |
| } |
| } |
| } |
| } |
| |
| // dialSerial connects to a list of addresses in sequence, returning |
| // either the first successful connection, or the first error. |
| func (sd *sysDialer) dialSerial(ctx context.Context, ras addrList) (Conn, error) { |
| var firstErr error // The error from the first address is most relevant. |
| |
| for i, ra := range ras { |
| select { |
| case <-ctx.Done(): |
| return nil, &OpError{Op: "dial", Net: sd.network, Source: sd.LocalAddr, Addr: ra, Err: mapErr(ctx.Err())} |
| default: |
| } |
| |
| dialCtx := ctx |
| if deadline, hasDeadline := ctx.Deadline(); hasDeadline { |
| partialDeadline, err := partialDeadline(time.Now(), deadline, len(ras)-i) |
| if err != nil { |
| // Ran out of time. |
| if firstErr == nil { |
| firstErr = &OpError{Op: "dial", Net: sd.network, Source: sd.LocalAddr, Addr: ra, Err: err} |
| } |
| break |
| } |
| if partialDeadline.Before(deadline) { |
| var cancel context.CancelFunc |
| dialCtx, cancel = context.WithDeadline(ctx, partialDeadline) |
| defer cancel() |
| } |
| } |
| |
| c, err := sd.dialSingle(dialCtx, ra) |
| if err == nil { |
| return c, nil |
| } |
| if firstErr == nil { |
| firstErr = err |
| } |
| } |
| |
| if firstErr == nil { |
| firstErr = &OpError{Op: "dial", Net: sd.network, Source: nil, Addr: nil, Err: errMissingAddress} |
| } |
| return nil, firstErr |
| } |
| |
| // dialSingle attempts to establish and returns a single connection to |
| // the destination address. |
| func (sd *sysDialer) dialSingle(ctx context.Context, ra Addr) (c Conn, err error) { |
| trace, _ := ctx.Value(nettrace.TraceKey{}).(*nettrace.Trace) |
| if trace != nil { |
| raStr := ra.String() |
| if trace.ConnectStart != nil { |
| trace.ConnectStart(sd.network, raStr) |
| } |
| if trace.ConnectDone != nil { |
| defer func() { trace.ConnectDone(sd.network, raStr, err) }() |
| } |
| } |
| la := sd.LocalAddr |
| switch ra := ra.(type) { |
| case *TCPAddr: |
| la, _ := la.(*TCPAddr) |
| c, err = sd.dialTCP(ctx, la, ra) |
| case *UDPAddr: |
| la, _ := la.(*UDPAddr) |
| c, err = sd.dialUDP(ctx, la, ra) |
| case *IPAddr: |
| la, _ := la.(*IPAddr) |
| c, err = sd.dialIP(ctx, la, ra) |
| case *UnixAddr: |
| la, _ := la.(*UnixAddr) |
| c, err = sd.dialUnix(ctx, la, ra) |
| default: |
| return nil, &OpError{Op: "dial", Net: sd.network, Source: la, Addr: ra, Err: &AddrError{Err: "unexpected address type", Addr: sd.address}} |
| } |
| if err != nil { |
| return nil, &OpError{Op: "dial", Net: sd.network, Source: la, Addr: ra, Err: err} // c is non-nil interface containing nil pointer |
| } |
| return c, nil |
| } |
| |
| // ListenConfig contains options for listening to an address. |
| type ListenConfig struct { |
| // If Control is not nil, it is called after creating the network |
| // connection but before binding it to the operating system. |
| // |
| // Network and address parameters passed to Control method are not |
| // necessarily the ones passed to Listen. For example, passing "tcp" to |
| // Listen will cause the Control function to be called with "tcp4" or "tcp6". |
| Control func(network, address string, c syscall.RawConn) error |
| |
| // KeepAlive specifies the keep-alive period for network |
| // connections accepted by this listener. |
| // If zero, keep-alives are enabled if supported by the protocol |
| // and operating system. Network protocols or operating systems |
| // that do not support keep-alives ignore this field. |
| // If negative, keep-alives are disabled. |
| KeepAlive time.Duration |
| } |
| |
| // Listen announces on the local network address. |
| // |
| // See func Listen for a description of the network and address |
| // parameters. |
| func (lc *ListenConfig) Listen(ctx context.Context, network, address string) (Listener, error) { |
| addrs, err := DefaultResolver.resolveAddrList(ctx, "listen", network, address, nil) |
| if err != nil { |
| return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: nil, Err: err} |
| } |
| sl := &sysListener{ |
| ListenConfig: *lc, |
| network: network, |
| address: address, |
| } |
| var l Listener |
| la := addrs.first(isIPv4) |
| switch la := la.(type) { |
| case *TCPAddr: |
| l, err = sl.listenTCP(ctx, la) |
| case *UnixAddr: |
| l, err = sl.listenUnix(ctx, la) |
| default: |
| return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: address}} |
| } |
| if err != nil { |
| return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: err} // l is non-nil interface containing nil pointer |
| } |
| return l, nil |
| } |
| |
| // ListenPacket announces on the local network address. |
| // |
| // See func ListenPacket for a description of the network and address |
| // parameters. |
| func (lc *ListenConfig) ListenPacket(ctx context.Context, network, address string) (PacketConn, error) { |
| addrs, err := DefaultResolver.resolveAddrList(ctx, "listen", network, address, nil) |
| if err != nil { |
| return nil, &OpError{Op: "listen", Net: network, Source: nil, Addr: nil, Err: err} |
| } |
| sl := &sysListener{ |
| ListenConfig: *lc, |
| network: network, |
| address: address, |
| } |
| var c PacketConn |
| la := addrs.first(isIPv4) |
| switch la := la.(type) { |
| case *UDPAddr: |
| c, err = sl.listenUDP(ctx, la) |
| case *IPAddr: |
| c, err = sl.listenIP(ctx, la) |
| case *UnixAddr: |
| c, err = sl.listenUnixgram(ctx, la) |
| default: |
| return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: address}} |
| } |
| if err != nil { |
| return nil, &OpError{Op: "listen", Net: sl.network, Source: nil, Addr: la, Err: err} // c is non-nil interface containing nil pointer |
| } |
| return c, nil |
| } |
| |
| // sysListener contains a Listen's parameters and configuration. |
| type sysListener struct { |
| ListenConfig |
| network, address string |
| } |
| |
| // Listen announces on the local network address. |
| // |
| // The network must be "tcp", "tcp4", "tcp6", "unix" or "unixpacket". |
| // |
| // For TCP networks, if the host in the address parameter is empty or |
| // a literal unspecified IP address, Listen listens on all available |
| // unicast and anycast IP addresses of the local system. |
| // To only use IPv4, use network "tcp4". |
| // The address can use a host name, but this is not recommended, |
| // because it will create a listener for at most one of the host's IP |
| // addresses. |
| // If the port in the address parameter is empty or "0", as in |
| // "127.0.0.1:" or "[::1]:0", a port number is automatically chosen. |
| // The Addr method of Listener can be used to discover the chosen |
| // port. |
| // |
| // See func Dial for a description of the network and address |
| // parameters. |
| // |
| // Listen uses context.Background internally; to specify the context, use |
| // ListenConfig.Listen. |
| func Listen(network, address string) (Listener, error) { |
| var lc ListenConfig |
| return lc.Listen(context.Background(), network, address) |
| } |
| |
| // ListenPacket announces on the local network address. |
| // |
| // The network must be "udp", "udp4", "udp6", "unixgram", or an IP |
| // transport. The IP transports are "ip", "ip4", or "ip6" followed by |
| // a colon and a literal protocol number or a protocol name, as in |
| // "ip:1" or "ip:icmp". |
| // |
| // For UDP and IP networks, if the host in the address parameter is |
| // empty or a literal unspecified IP address, ListenPacket listens on |
| // all available IP addresses of the local system except multicast IP |
| // addresses. |
| // To only use IPv4, use network "udp4" or "ip4:proto". |
| // The address can use a host name, but this is not recommended, |
| // because it will create a listener for at most one of the host's IP |
| // addresses. |
| // If the port in the address parameter is empty or "0", as in |
| // "127.0.0.1:" or "[::1]:0", a port number is automatically chosen. |
| // The LocalAddr method of PacketConn can be used to discover the |
| // chosen port. |
| // |
| // See func Dial for a description of the network and address |
| // parameters. |
| // |
| // ListenPacket uses context.Background internally; to specify the context, use |
| // ListenConfig.ListenPacket. |
| func ListenPacket(network, address string) (PacketConn, error) { |
| var lc ListenConfig |
| return lc.ListenPacket(context.Background(), network, address) |
| } |