internal: example flag.Parse() and comments (#2526)

examples/features/metadata/client/main.go

@@ -284,6 +284,7 @@ func bidirectionalWithMetadata(c pb.EchoClient, message string) {
 const message = "this is examples/metadata"
 
 func main() {
+	flag.Parse()
 	// Set up a connection to the server.
 	conn, err := grpc.Dial(*addr, grpc.WithInsecure())
 	if err != nil {

examples/features/metadata/server/main.go

@@ -194,6 +194,7 @@ func (s *server) BidirectionalStreamingEcho(stream pb.Echo_BidirectionalStreamin
 }
 
 func main() {
+	flag.Parse()
 	rand.Seed(time.Now().UnixNano())
 	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
 	if err != nil {

examples/features/multiplex/client/main.go

@@ -16,10 +16,12 @@
  *
  */
 
+// Binary client is an example client.
 package main
 
 import (
 	"context"
+	"flag"
 	"fmt"
 	"log"
 	"time"
@@ -29,9 +31,7 @@ import (
 	hwpb "google.golang.org/grpc/examples/helloworld/helloworld"
 )
 
-const (
-	address = "localhost:50051"
-)
+var addr = flag.String("addr", "localhost:50051", "the address to connect to")
 
 // callSayHello calls SayHello on c with the given name, and prints the
 // response.
@@ -56,8 +56,9 @@ func callUnaryEcho(client ecpb.EchoClient, message string) {
 }
 
 func main() {
+	flag.Parse()
 	// Set up a connection to the server.
-	conn, err := grpc.Dial(address, grpc.WithInsecure())
+	conn, err := grpc.Dial(*addr, grpc.WithInsecure())
 	if err != nil {
 		log.Fatalf("did not connect: %v", err)
 	}

examples/features/multiplex/server/main.go

@@ -16,10 +16,13 @@
  *
  */
 
+// Binary server is an example server.
 package main
 
 import (
 	"context"
+	"flag"
+	"fmt"
 	"log"
 	"net"
 
@@ -30,9 +33,7 @@ import (
 	"google.golang.org/grpc/status"
 )
 
-const (
-	port = ":50051"
-)
+var port = flag.Int("port", 50051, "the port to serve on")
 
 // hwServer is used to implement helloworld.GreeterServer.
 type hwServer struct{}
@@ -61,10 +62,13 @@ func (s *ecServer) BidirectionalStreamingEcho(ecpb.Echo_BidirectionalStreamingEc
 }
 
 func main() {
-	lis, err := net.Listen("tcp", port)
+	flag.Parse()
+	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
 	if err != nil {
 		log.Fatalf("failed to listen: %v", err)
 	}
+	fmt.Printf("server listening at %v\n", lis.Addr())
+
 	s := grpc.NewServer()
 
 	// Register Greeter on the server.