When I open a standalone DDMS besides Eclipse, it generates the below error.

hieund@hieund:~$ ddms
01:51:58 E/ddms: Could not open Selected VM debug port (8700). Make sure you do not have another instance of DDMS or of the eclipse plugin running. If it's being used by something else, choose a new port number in the preferences.

(DDMS:6904): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -5 and height 17

(DDMS:6904): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -5 and height 17
01:52:18 E/DDMS: device offline
com.android.ddmlib.AdbCommandRejectedException: device offline
    at com.android.ddmlib.AdbHelper.setDevice(AdbHelper.java:736)
    at com.android.ddmlib.AdbHelper.executeRemoteCommand(AdbHelper.java:373)
    at com.android.ddmlib.Device.executeShellCommand(Device.java:364)
    at com.android.ddmuilib.SysinfoPanel.loadFromDevice(SysinfoPanel.java:159)
    at com.android.ddmuilib.SysinfoPanel.deviceSelected(SysinfoPanel.java:126)
    at com.android.ddmuilib.SelectionDependentPanel.deviceSelected(SelectionDependentPanel.java:52)
    at com.android.ddms.UIThread.selectionChanged(UIThread.java:1721)
    at com.android.ddmuilib.DevicePanel.notifyListeners(DevicePanel.java:752)
    at com.android.ddmuilib.DevicePanel.notifyListeners(DevicePanel.java:740)
    at com.android.ddmuilib.DevicePanel.access$1100(DevicePanel.java:56)
    at com.android.ddmuilib.DevicePanel$1.widgetSelected(DevicePanel.java:357)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at com.android.ddms.UIThread.runUI(UIThread.java:517)
    at com.android.ddms.Main.main(Main.java:116)

01:52:32 E/ddms: shutting down due to uncaught exception
01:52:32 E/ddms: Failed to execute runnable (java.lang.ArrayIndexOutOfBoundsException: -1)
org.eclipse.swt.SWTException: Failed to execute runnable (java.lang.ArrayIndexOutOfBoundsException: -1)
    at org.eclipse.swt.SWT.error(Unknown Source)
    at org.eclipse.swt.SWT.error(Unknown Source)
    at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Unknown Source)
    at org.eclipse.swt.widgets.Display.runAsyncMessages(Unknown Source)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
    at com.android.ddms.UIThread.runUI(UIThread.java:517)
    at com.android.ddms.Main.main(Main.java:116)
Caused by: java.lang.ArrayIndexOutOfBoundsException: -1
    at org.eclipse.jface.viewers.AbstractTableViewer$VirtualManager.resolveElement(AbstractTableViewer.java:100)
    at org.eclipse.jface.viewers.AbstractTableViewer$1.handleEvent(AbstractTableViewer.java:70)
    at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source)
    at org.eclipse.swt.widgets.Table.checkData(Unknown Source)
    at org.eclipse.swt.widgets.Table.cellDataProc(Unknown Source)
    at org.eclipse.swt.widgets.Display.cellDataProc(Unknown Source)
    at org.eclipse.swt.internal.gtk.OS._gtk_list_store_append(Native Method)
    at org.eclipse.swt.internal.gtk.OS.gtk_list_store_append(Unknown Source)
    at org.eclipse.swt.widgets.Table.setItemCount(Unknown Source)
    at org.eclipse.jface.viewers.TableViewer.doSetItemCount(TableViewer.java:217)
    at org.eclipse.jface.viewers.AbstractTableViewer.internalVirtualRefreshAll(AbstractTableViewer.java:661)
    at org.eclipse.jface.viewers.AbstractTableViewer.internalRefresh(AbstractTableViewer.java:635)
    at org.eclipse.jface.viewers.AbstractTableViewer.internalRefresh(AbstractTableViewer.java:620)
    at org.eclipse.jface.viewers.StructuredViewer$7.run(StructuredViewer.java:1430)
    at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1365)
    at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1328)
    at org.eclipse.jface.viewers.StructuredViewer.refresh(StructuredViewer.java:1428)
    at org.eclipse.jface.viewers.ColumnViewer.refresh(ColumnViewer.java:537)
    at org.eclipse.jface.viewers.StructuredViewer.refresh(StructuredViewer.java:1387)
    at com.android.ddmuilib.logcat.LogCatPanel$LogCatTableRefresherTask.run(LogCatPanel.java:1000)
    at org.eclipse.swt.widgets.RunnableLock.run(Unknown Source)
    ... 5 more

I tried to change port for DDMS in Eclipse but it still doesn't work.