First commit

Ch03/DaytimeServer.go

@@ -0,0 +1,38 @@
+/* DaytimeServer
+ */
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"time"
+)
+
+func main() {
+
+	service := ":1200"
+	tcpAddr, err := net.ResolveTCPAddr("tcp", service)
+	checkError(err)
+
+	listener, err := net.ListenTCP("tcp", tcpAddr)
+	checkError(err)
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			continue
+		}
+
+		daytime := time.Now().String()
+		conn.Write([]byte(daytime)) // don't care about return value
+		conn.Close()                // we're finished with this client
+	}
+}
+
+func checkError(err error) {
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())
+		os.Exit(1)
+	}
+}

Ch03/EchoClient.go

@@ -0,0 +1,49 @@
+/* EchoClient
+ */
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"runtime"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprint(os.Stderr, "Usage: ", os.Args[0], " host:port\n")
+		// fmt.Println("Usage: ", os.Args[0], "host:port")
+		os.Exit(1)
+	}
+	service := os.Args[1]
+
+	conn, err := net.Dial("tcp", service)
+	checkError("Dial", err)
+
+	for n := 0; n < 10; n++ {
+		conn.Write([]byte("Hello " + string(n+48)))
+
+		var buf [512]byte
+		n, err := conn.Read(buf[0:])
+		checkError("Read", err)
+
+		fmt.Println(string(buf[0:n]))
+	}
+	os.Exit(0)
+}
+
+func checkError(errStr string, err error) {
+	if err != nil {
+		fmt.Fprint(os.Stderr, errStr, err.Error())
+		//log.Exit(errStr+":",  err.Error())
+		_, file, line, ok := runtime.Caller(1)
+		if ok {
+			fmt.Println("Line number", file, line)
+		}
+		os.Exit(1)
+		/*
+			fmt.Println("Fatal error ", err.Error())
+			os.Exit(1)
+		*/
+	}
+}

Ch03/GetHeadInfo.go

@@ -0,0 +1,42 @@
+/* GetHeadInfo
+ */
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s host:port ", os.Args[0])
+		os.Exit(1)
+	}
+	service := os.Args[1]
+
+	tcpAddr, err := net.ResolveTCPAddr("tcp4", service)
+	checkError(err)
+
+	conn, err := net.DialTCP("tcp", nil, tcpAddr)
+	checkError(err)
+
+	_, err = conn.Write([]byte("HEAD / HTTP/1.0\r\n\r\n"))
+	checkError(err)
+
+	//result, err := readFully(conn)
+	result, err := ioutil.ReadAll(conn)
+	checkError(err)
+
+	fmt.Println(string(result))
+
+	os.Exit(0)
+}
+
+func checkError(err error) {
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())
+		os.Exit(1)
+	}
+}

Ch03/IP.go

@@ -0,0 +1,26 @@
+/* IP
+ */
+
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s ip-addr\n", os.Args[0])
+		os.Exit(1)
+	}
+	name := os.Args[1]
+
+	addr := net.ParseIP(name)
+	if addr == nil {
+		fmt.Println("Invalid address")
+	} else {
+		fmt.Println("The address is ", addr.String())
+	}
+	os.Exit(0)
+}

Ch03/IPDaytimeClient.go

@@ -0,0 +1,38 @@
+/* IPDaytimeClient
+ */
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Println("Usage: ", os.Args[0], "host:port")
+		os.Exit(1)
+	}
+	service := os.Args[1]
+
+	conn, err := net.Dial("udp", service)
+	checkError(err)
+
+	_, err = conn.Write([]byte("anything"))
+	checkError(err)
+
+	var buf [512]byte
+	n, err := conn.Read(buf[0:])
+	checkError(err)
+
+	fmt.Println(string(buf[0:n]))
+
+	os.Exit(0)
+}
+
+func checkError(err error) {
+	if err != nil {
+		fmt.Println("Fatal error ", err.Error())
+		os.Exit(1)
+	}
+}

Ch03/IPGetHeadInfo.go

@@ -0,0 +1,58 @@
+/* IPGetHeadInfo
+ */
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s host:port", os.Args[0])
+		os.Exit(1)
+	}
+	service := os.Args[1]
+
+	conn, err := net.Dial("tcp", service)
+	checkError(err)
+
+	_, err = conn.Write([]byte("HEAD / HTTP/1.0\r\n\r\n"))
+	checkError(err)
+
+	result, err := readFully(conn)
+	//result, err := io.readAll(conn)
+	checkError(err)
+
+	fmt.Println(string(result))
+
+	os.Exit(0)
+}
+
+func checkError(err error) {
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Fatal error: %s", err.Error())
+		os.Exit(1)
+	}
+}
+
+func readFully(conn net.Conn) ([]byte, error) {
+	defer conn.Close()
+
+	result := bytes.NewBuffer(nil)
+	var buf [512]byte
+	for {
+		n, err := conn.Read(buf[0:])
+		result.Write(buf[0:n])
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return nil, err
+		}
+	}
+	return result.Bytes(), nil
+}

Ch03/IPv4Mask.go

@@ -0,0 +1,33 @@
+/* IPv4Mask
+ */
+
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s dotted-ip-addr\n", os.Args[0])
+		os.Exit(1)
+	}
+	dotAddr := os.Args[1]
+
+	addr := net.ParseIP(dotAddr)
+	if addr == nil {
+		fmt.Println("Invalid address")
+		os.Exit(1)
+	}
+	mask := addr.DefaultMask()
+	network := addr.Mask(mask)
+	ones, bits := mask.Size()
+	fmt.Println("Address is ", addr.String(),
+		"\nDefault mask length is ", bits,
+		"\nLeading ones count is ", ones,
+		"\nMask is (hex) ", mask.String(),
+		"\nNetwork is ", network.String())
+	os.Exit(0)
+}

Ch03/LookupHost.go

@@ -0,0 +1,29 @@
+/* LookupHost
+ */
+
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s hostname\n", os.Args[0])
+		os.Exit(1)
+	}
+	name := os.Args[1]
+
+	addrs, err := net.LookupHost(name)
+	if err != nil {
+		fmt.Println("Error: ", err.Error())
+		os.Exit(2)
+	}
+
+	for _, s := range addrs {
+		fmt.Println(s)
+	}
+	os.Exit(0)
+}

Ch03/LookupPort.go

@@ -0,0 +1,30 @@
+/* LookupPort
+ */
+
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 3 {
+		fmt.Fprintf(os.Stderr,
+			"Usage: %s network-type service\n",
+			os.Args[0])
+		os.Exit(1)
+	}
+	networkType := os.Args[1]
+	service := os.Args[2]
+
+	port, err := net.LookupPort(networkType, service)
+	if err != nil {
+		fmt.Println("Error: ", err.Error())
+		os.Exit(2)
+	}
+
+	fmt.Println("Service port ", port)
+	os.Exit(0)
+}

Ch03/Mask.go

@@ -0,0 +1,35 @@
+/* Mask
+ */
+
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+)
+
+func main() {
+	if len(os.Args) != 4 {
+		fmt.Fprintf(os.Stderr, "Usage: %s dotted-ip-addr ones bits\n", os.Args[0])
+		os.Exit(1)
+	}
+	dotAddr := os.Args[1]
+	ones, _ := strconv.Atoi(os.Args[2])
+	bits, _ := strconv.Atoi(os.Args[3])
+
+	addr := net.ParseIP(dotAddr)
+	if addr == nil {
+		fmt.Println("Invalid address")
+		os.Exit(1)
+	}
+	mask := net.CIDRMask(ones, bits)
+	network := addr.Mask(mask)
+	fmt.Println("Address is ", addr.String(),
+		"\nMask length is ", bits,
+		"\nLeading ones count is ", ones,
+		"\nMask is (hex) ", mask.String(),
+		"\nNetwork is ", network.String())
+	os.Exit(0)
+}