java实现hello/hi的简单的网络聊天程序与ServerSocket调用栈跟踪

java实现hello/hi的简单的网络聊天程序

• 网络聊天采用TCP协议通过java实现

  import java.io.*;
  import java.net.Socket;
  
  public class Client {
      public static void main(String[] args) throws Exception{
        
          Socket socket = new Socket("192.168.31.68", 6666);
  
          BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
          String s = reader.readLine();
  
          OutputStream outputStream = socket.getOutputStream();
          BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(outputStream));
          writer.write(s);
          writer.newLine();
          writer.flush();
          socket.close();
      }
  }
  
  

  import java.io.InputStream;
  import java.net.InetAddress;
  import java.net.ServerSocket;
  import java.net.Socket;
  
  
  public class SeverDemo {
      public static void main(String[] args) throws Exception{
       
          ServerSocket serverSocket = new ServerSocket(6666);
          Object i = null;
         
          while(true) {
              Socket socket = serverSocket.accept(); 
             
              InputStream inputStream = socket.getInputStream();
              
              byte[] bytes = new byte[1024];
              int len = inputStream.read(bytes);
              String s = new String(bytes, 0, len);
              InetAddress address = socket.getInetAddress();
              System.out.println("from " + address.getHostAddress() + ": " + s);
           
              socket.close();
          }
      }
  
  
  

• Server
  

• Client
  

ServerSocket调用栈跟踪

• 该图片描述的是socket0函数调用栈的关系
• 从图中可以看出java从 serversocket -> 调用socketImpt -> abstractPlainSocketImpl -> DualStackSocketPlainImpl-> DualStackPlainImplt_socket0
• 最后调用的是java中的native函数，可以在openjdk中看到（我使用的版本是openjdk 8.0）

// windows/native/java/net/DualStackPlainSocketImpl.c
/*
 * Class:     java_net_DualStackPlainSocketImpl
 * Method:    socket0
 * Signature: (ZZ)I
 */
JNIEXPORT jint JNICALL Java_java_net_DualStackPlainSocketImpl_socket0
  (JNIEnv *env, jclass clazz, jboolean stream, jboolean v6Only /*unused*/) {
    int fd, rv, opt=0;
  
//细看可以发现，这就是我们熟悉的linux下网络编程socket的api
    fd = NET_Socket(AF_INET6, (stream ? SOCK_STREAM : SOCK_DGRAM), 0);
  
  	if (fd == INVALID_SOCKET) {
        NET_ThrowNew(env, WSAGetLastError(), "create");
        return -1;
    }

    rv = setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, (char *) &opt, sizeof(opt));
    if (rv == SOCKET_ERROR) {
        NET_ThrowNew(env, WSAGetLastError(), "create");
    }

    SetHandleInformation((HANDLE)(UINT_PTR)fd, HANDLE_FLAG_INHERIT, FALSE);

    return fd;
}

• 该图片是listen函数的调用栈关系

• ServerSocket -> abstractPlaninSocketImpl -> DualStackSocketPlainImpl-> DualStackPlainImplt_listen0

• native关键字声明的c源码如下

  /*
   * Class:     java_net_DualStackPlainSocketImpl
   * Method:    listen0
   * Signature: (II)V
   */
  JNIEXPORT void JNICALL Java_java_net_DualStackPlainSocketImpl_listen0
    (JNIEnv *env, jclass clazz, jint fd, jint backlog) {
      if (listen(fd, backlog) == SOCKET_ERROR) {
          NET_ThrowNew(env, WSAGetLastError(), "listen failed");
      }
  }
  
  

• 该图片为bind函数的调用栈关系
• ServerSocket -> abstractPlaninSocketImpl -> DualStackSocketPlainImpl-> DualStackPlainImplt_bind0
• native关键字声明的c源码如下

/*
 * Class:     java_net_DualStackPlainSocketImpl
 * Method:    bind0
 * Signature: (ILjava/net/InetAddress;I)V
 */
JNIEXPORT void JNICALL Java_java_net_DualStackPlainSocketImpl_bind0
  (JNIEnv *env, jclass clazz, jint fd, jobject iaObj, jint port,
   jboolean exclBind)
{
    SOCKETADDRESS sa;
    int rv;
    int sa_len = sizeof(sa);

    if (NET_InetAddressToSockaddr(env, iaObj, port, (struct sockaddr *)&sa,
                                 &sa_len, JNI_TRUE) != 0) {
      return;
    }

    rv = NET_WinBind(fd, (struct sockaddr *)&sa, sa_len, exclBind);

    if (rv == SOCKET_ERROR)
        NET_ThrowNew(env, WSAGetLastError(), "JVM_Bind");
}

• 该图片为accept函数的调用栈关系
• ServerSocket -> abstractPlaninSocketImpl -> DualStackSocketPlainImpl-> DualStackPlainImplt_accept0

JNIEXPORT jint JNICALL Java_java_net_DualStackPlainSocketImpl_accept0
  (JNIEnv *env, jclass clazz, jint fd, jobjectArray isaa) {
    int newfd, port=0;
    jobject isa;
    jobject ia;
    SOCKETADDRESS sa;
    int len = sizeof(sa);

    memset((char *)&sa, 0, len);
    newfd = accept(fd, (struct sockaddr *)&sa, &len);

    if (newfd == INVALID_SOCKET) {
        if (WSAGetLastError() == -2) {
            JNU_ThrowByName(env, JNU_JAVAIOPKG "InterruptedIOException",
                            "operation interrupted");
        } else {
            JNU_ThrowByName(env, JNU_JAVANETPKG "SocketException",
                            "socket closed");
        }
        return -1;
    }

    ia = NET_SockaddrToInetAddress(env, (struct sockaddr *)&sa, &port);
    isa = (*env)->NewObject(env, isa_class, isa_ctorID, ia, port);
    (*env)->SetObjectArrayElement(env, isaa, 0, isa);

    return newfd;
}

Serversocket总结

• java底层也是调用linux 网络api实现网络通信的
• java中Serversocket创建时就对函数进行了socket和bind和listen操作，一个函数封装了linux下3个api
• java中的accept对应与linux下accpet函数
• Java中Socket客户端也是类似的情况，就不做重复分析。