Update tcp_basic example

Author: devlights

examples/singleapp/socket/README.md

@@ -0,0 +1,4 @@
+# サンプルリスト
+
+- [TCP:基本パターン](./tcp_basic/)
+  - 一番基本的なパターン

examples/singleapp/socket/tcp_basic/Taskfile.yml

@@ -1,21 +1,32 @@
 version: '3'
 
 tasks:
-  build:
+  default:
     cmds:
-      - (cd client; go build)
-      - (cd server; go build)
+      - task: run
   run:
     cmds:
-      - task: build
+      - task: build-server
+      - task: build-client
       - task: start-server
       - task: run-client
+      - task: kill-server
+  build-server:
+    dir: server
+    cmds:
+      - go build
+  build-client:
+    dir: client
+    cmds:
+      - go build
   start-server:
+    dir: server
     cmds:
-      - (cd server; ./server)
+      - ./server &
   run-client:
+    dir: client
     cmds:
-      - (cd client; ./client)
+      - ./client
   kill-server:
     cmds:
       - pkill server

examples/singleapp/socket/tcp_basic/client/main.go

@@ -22,61 +22,47 @@ import (
 )
 
 var (
-	appLog = log.New(os.Stdout, "[client]", 0)
-	errLog = log.New(os.Stderr, "[client]", 0)
+	appLog = log.New(os.Stdout, "[client] ", 0)
+	errLog = log.New(os.Stderr, "[client] ", 0)
 )
 
-func main() {
-	//
-	// 接続
-	//
+func connect(protocol, localAddr, remoteAddr string) (*net.TCPConn, error) {
 	var (
 		getAddr = net.ResolveTCPAddr
-		laddr   = errs.Forget(getAddr("tcp", "localhost:"))
-		raddr   = errs.Forget(getAddr("tcp", "localhost:8888"))
+		laddr   = errs.Forget(getAddr(protocol, localAddr))
+		raddr   = errs.Forget(getAddr(protocol, remoteAddr))
 		conn    *net.TCPConn
 		err     error
 	)
 
 	conn, err = net.DialTCP("tcp", laddr, raddr)
 	if err != nil {
-		errLog.Fatal(err)
+		return nil, err
 	}
-	defer conn.Close()
-
-	appLog.Printf("connected to: %s\n", conn.RemoteAddr())
 
-	//
-	// 送信
-	//
-	var (
-		message = []byte("hello world")
-	)
+	return conn, err
+}
 
-	_, err = conn.Write(message)
+func send(conn *net.TCPConn, b []byte) error {
+	_, err := conn.Write(b)
 	if err != nil {
-		errLog.Printf("error at conn.Write (%v)", err)
-		return
+		return err
 	}
 
-	err = conn.CloseWrite()
-	if err != nil {
-		errLog.Printf("error at conn.Write (%v)", err)
-		return
-	}
+	return nil
+}
 
-	//
-	// 受信
-	//
+func recv(conn *net.TCPConn) ([]byte, error) {
 	var (
 		buf       = new(bytes.Buffer)
 		bytesRead int
 	)
 
 	for {
 		var (
-			chunk     = make([]byte, 1)
+			chunk     = make([]byte, 3)
 			chunkSize int
+			err       error
 		)
 
 		chunkSize, err = conn.Read(chunk)
@@ -89,22 +75,62 @@ func main() {
 				break
 			}
 
-			errLog.Printf("error at conn.Read (%v)", err)
-			return
+			return nil, err
 		}
 
 		if chunkSize == 0 {
-			appLog.Printf("closed by remote")
-			return
+			return nil, errors.New("closed by remote")
 		}
 
 		bytesRead += chunkSize
 		buf.Write(chunk)
 	}
-	appLog.Printf("%d bytes recv", bytesRead)
 
+	return buf.Bytes()[:bytesRead], nil
+}
+
+func main() {
+	//
+	// 接続
+	//
+	conn, err := connect("tcp", "localhost:", "localhost:8888")
+	if err != nil {
+		errLog.Printf("error at connect (%v)", err)
+	}
+	defer conn.Close()
+
+	appLog.Printf("connected to: %s\n", conn.RemoteAddr())
+
+	//
+	// 送信
+	//
 	var (
-		data = buf.Bytes()[:bytesRead]
+		message = []byte("hello world")
 	)
+
+	err = send(conn, message)
+	if err != nil {
+		errLog.Printf("error at conn.Write (%v)", err)
+		return
+	}
+	appLog.Printf("%d bytes send", len(message))
+
+	// 対向先にEOFを伝えるために無理やり送信側ストリームを閉じる
+	// (本来は、通信メッセージ毎の構造規約があるはずなので、このようにすることは無い。サンプルなので。)
+	err = conn.CloseWrite()
+	if err != nil {
+		errLog.Printf("error at conn.Write (%v)", err)
+		return
+	}
+	appLog.Println("notify EOF (conn.CloseWrite)")
+
+	//
+	// 受信
+	//
+	data, err := recv(conn)
+	if err != nil {
+		errLog.Printf("error at recv (%v)", err)
+	}
+	appLog.Printf("%d bytes recv", len(data))
 	appLog.Printf("recv: %s\n", data)
 }

examples/singleapp/socket/tcp_basic/server/main.go

@@ -24,10 +24,56 @@ import (
 )
 
 var (
-	appLog = log.New(os.Stdout, "[server]", 0)
-	errLog = log.New(os.Stderr, "[server]", 0)
+	appLog = log.New(os.Stdout, "[server] ", 0)
+	errLog = log.New(os.Stderr, "[server] ", 0)
 )
 
+func send(conn *net.TCPConn, b []byte) error {
+	_, err := conn.Write(b)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func recv(conn *net.TCPConn) ([]byte, error) {
+	var (
+		buf       = new(bytes.Buffer)
+		bytesRead int
+	)
+
+	for {
+		var (
+			chunk     = make([]byte, 10)
+			chunkSize int
+			err       error
+		)
+
+		chunkSize, err = conn.Read(chunk)
+		appLog.Printf("chunk recv: %dbyte(s)\terr:%v", chunkSize, err)
+
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				bytesRead += chunkSize
+				buf.Write(chunk)
+				break
+			}
+
+			return nil, err
+		}
+
+		if chunkSize == 0 {
+			return nil, errors.New("closed by remote")
+		}
+
+		bytesRead += chunkSize
+		buf.Write(chunk)
+	}
+
+	return buf.Bytes()[:bytesRead], nil
+}
+
 func main() {
 	//
 	// 起動
@@ -90,44 +136,11 @@ func main() {
 			//
 			// 受信
 			//
-			var (
-				buf       = new(bytes.Buffer)
-				bytesRead int
-			)
-
-			for {
-				var (
-					chunk     = make([]byte, 1)
-					chunkSize int
-				)
-
-				chunkSize, err = conn.Read(chunk)
-				appLog.Printf("chunk recv: %dbyte(s)\terr:%v", chunkSize, err)
-
-				if err != nil {
-					if errors.Is(err, io.EOF) {
-						bytesRead += chunkSize
-						buf.Write(chunk)
-						break
-					}
-
-					appLog.Printf("error at conn.Read (%v)", err)
-					return
-				}
-
-				if chunkSize == 0 {
-					appLog.Printf("closed by remote")
-					return
-				}
-
-				bytesRead += chunkSize
-				buf.Write(chunk)
+			data, err := recv(conn)
+			if err != nil {
+				errLog.Printf("error at recv (%v)", err)
 			}
-			appLog.Printf("%d bytes recv", bytesRead)
-
-			var (
-				data = buf.Bytes()[:bytesRead]
-			)
+			appLog.Printf("%d bytes recv", len(data))
 			appLog.Printf("recv: %s\n", data)
 
 			//
@@ -137,17 +150,25 @@ func main() {
 				message = bytes.ToUpper(data)
 			)
 
-			_, err = conn.Write(message)
+			err = send(conn, message)
 			if err != nil {
-				errLog.Printf("error at client writeto (%v)", err)
+				errLog.Printf("error at send (%v)", err)
 				return
 			}
+			appLog.Printf("%d bytes send", len(message))
 
+			// 対向先にEOFを伝えるために無理やり送信側ストリームを閉じる
+			// (本来は、通信メッセージ毎の構造規約があるはずなので、このようにすることは無い。サンプルなので。)
+			//
+			// サーバ側の今回の実装では、これを行わなくても defer conn.Close() で切断するので対向先にEOFが通知されるが一応入れている			
 			err = conn.CloseWrite()
 			if err != nil {
 				errLog.Printf("error at conn closewrite (%v)", err)
 				return
 			}
+			appLog.Println("notify EOF (conn.CloseWrite)")
+
+
 		}()
 	}
 }