无法连接到xmpp服务器

Question

我尝试使用xmpp连接到Gmail服务器。它工作正常。但是当我尝试连接本地xmpp服务器时它无效。这是片段

// Create a connection
    SmackConfiguration.setPacketReplyTimeout(500);

    ConnectionConfiguration connConfig =
            new ConnectionConfiguration("ubuntu", 5222,"ubuntu");
    XMPPConnection connection = new XMPPConnection(connConfig);

    try {
        connection.connect();
        Log.i("XMPPClient", "[SettingsDialog] Connected to " + connection.getHost());
    } catch (XMPPException ex) {
        Log.e("XMPPClient", "[SettingsDialog] Failed to connect to " + connection.getHost());
        Log.e("XMPPClient", ex.toString());
        xmppClient.setConnection(null);
    }