go.net/ipv4: update package documentation
- fix more multicasting section as pointed out in go.net/ipv6 review
- simplify example codes
- do word alignment; s/multicast group address/multicast group/
R=dave
CC=golang-dev
https://golang.org/cl/10322043
diff --git a/ipv4/doc.go b/ipv4/doc.go
index ffdb9ff..576cd83 100644
--- a/ipv4/doc.go
+++ b/ipv4/doc.go
@@ -36,12 +36,10 @@
// The outgoing packets will be labeled DiffServ assured forwarding
// class 1 low drop precedence, as known as AF11 packets.
//
-// err := ipv4.NewConn(c).SetTOS(DiffServAF11)
-// if err != nil {
+// if err := ipv4.NewConn(c).SetTOS(DiffServAF11); err != nil {
// // error handling
// }
-// _, err = c.Write(data)
-// if err != nil {
+// if _, err := c.Write(data); err != nil {
// // error handling
// }
// }(c)
@@ -54,7 +52,7 @@
// net.IPconn which are created as network connections that use the
// IPv4 transport. A few network facilities must be prepared before
// you begin multicasting, at a minimum joining network interfaces and
-// group addresses.
+// multicast groups.
//
// en0, err := net.InterfaceByName("en0")
// if err != nil {
@@ -75,19 +73,17 @@
// }
// defer c.Close()
//
-// Second, the application joins groups, starts listening to the
-// group addresses on the specified network interfaces. Note that
-// the service port for transport layer protocol does not matter with
-// this operation as joining groups affects only network and link
-// layer protocols, such as IPv4 and Ethernet.
+// Second, the application joins multicast groups, starts listening to
+// the groups on the specified network interfaces. Note that the
+// service port for transport layer protocol does not matter with this
+// operation as joining groups affects only network and link layer
+// protocols, such as IPv4 and Ethernet.
//
// p := ipv4.NewPacketConn(c)
-// err = p.JoinGroup(en0, &net.UDPAddr{IP: group})
-// if err != nil {
+// if err := p.JoinGroup(en0, &net.UDPAddr{IP: group}); err != nil {
// // error handling
// }
-// err = p.JoinGroup(en1, &net.UDPAddr{IP: group})
-// if err != nil {
+// if err := p.JoinGroup(en1, &net.UDPAddr{IP: group}); err != nil {
// // error handling
// }
//
@@ -97,8 +93,7 @@
// SetControlMessage of ipv4.PacketConn is used to enable control
// message transmissons.
//
-// err = p.SetControlMessage(ipv4.FlagDst, true)
-// if err != nil {
+// if err := p.SetControlMessage(ipv4.FlagDst, true); err != nil {
// // error handling
// }
//
@@ -125,19 +120,16 @@
//
// p.SetTOS(DiffServCS0)
// p.SetTTL(16)
-// _, err = p.WriteTo(data, nil, src)
-// if err != nil {
+// if _, err := p.WriteTo(data, nil, src); err != nil {
// // error handling
// }
// dst := &net.UDPAddr{IP: group, Port: 1024}
// for _, ifi := range []*net.Interface{en0, en1} {
-// err := p.SetMulticastInterface(ifi)
-// if err != nil {
+// if err := p.SetMulticastInterface(ifi); err != nil {
// // error handling
// }
// p.SetMulticastTTL(2)
-// _, err = p.WriteTo(data, nil, dst)
-// if err != nil {
+// if _, err := p.WriteTo(data, nil, dst); err != nil {
// // error handling
// }
// }
@@ -146,10 +138,10 @@
//
// More multicasting
//
-// An application that uses PacketConn or RawConn might join the
-// multiple group addresses. For example, a UDP listener with port
-// 1024 might join two different groups across over two different
-// network interfaces by using:
+// An application that uses PacketConn or RawConn may join multiple
+// multicast groups. For example, a UDP listener with port 1024 might
+// join two different groups across over two different network
+// interfaces by using:
//
// c, err := net.ListenPacket("udp4", "0.0.0.0:1024")
// if err != nil {
@@ -157,21 +149,18 @@
// }
// defer c.Close()
// p := ipv4.NewPacketConn(c)
-// err = p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)})
-// if err != nil {
+// if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
// // error handling
// }
-// err = p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 249)})
-// if err != nil {
+// if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 249)}); err != nil {
// // error handling
// }
-// err = p.JoinGroup(en1, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 249)})
-// if err != nil {
+// if err := p.JoinGroup(en1, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 249)}); err != nil {
// // error handling
// }
//
// It is possible for multiple UDP listeners that listen on the same
-// UDP port to join the same group address. The net package will
+// UDP port to join the same multicast group. The net package will
// provide a socket that listens to a wildcard address with reusable
// UDP port when an appropriate multicast address prefix is passed to
// the net.ListenPacket or net.ListenUDP.
@@ -187,25 +176,21 @@
// }
// defer c2.Close()
// p1 := ipv4.NewPacketConn(c1)
-// err = p1.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)})
-// if err != nil {
+// if err := p1.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
// // error handling
// }
// p2 := ipv4.NewPacketConn(c2)
-// err = p2.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)})
-// if err != nil {
+// if err := p2.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
// // error handling
// }
//
// Also it is possible for the application to leave or rejoin a
// multicast group on the network interface.
//
-// err = p.LeaveGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)})
-// if err != nil {
+// if err := p.LeaveGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 248)}); err != nil {
// // error handling
// }
-// err = p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 250)})
-// if err != nil {
+// if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.IPv4(224, 0, 0, 250)}); err != nil {
// // error handling
// }
package ipv4
