roscore运行报错Unable to contact my own server

　大概几天没有运行ＲＯＳ了，今天运行一下出现以下错误，在此记录一下

zztsj@tsj:~$ roscore
... logging to /home/zztsj/.ros/log/3455db8a-1536-11eb-9296-9822efa1466f/roslaunch-tsj-8025.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

RLException: Unable to contact my own server at [http://tsj:40035/].
This usually means that the network is not configured properly.
                                                                                          
A common cause is that the machine cannot ping itself.  Please check                      
for errors by running:                                                                    
                                                                                          
        ping tsj                                                                          
                                                                                          
For more tips, please see                                                                 
                                                                                          
        http://wiki.ros.org/ROS/NetworkSetup                                              
                                                                                          
The traceback for the exception was written to the log file

解决方法如下：

进入到配置文件

vim ~/.bashrc

加入以下两段代码

1  export ROS_HOSTNAME=localhost
2 export ROS_MASTER_URI=http://localhost:11311

更新环境变量

source ~/.bashrc

就顺利解决了，再次启动就可以正常的跑起来了。

可到官网去查找方法：http://wiki.ros.org/ROS/NetworkSetup

rosrun rqt_reconfigure rqt_reconfigure时出现PluginManager._load_plugin() could not load plugin

在进行ros动态参数配置过程中,运行rosrun rqt_reconfigure rqt_reconfigure

出现一下问题

PluginManager._load_plugin() could not load plugin "rqt_reconfigure/Param":
Traceback (most recent call last):
  File "/opt/ros/melodic/lib/python2.7/dist-packages/qt_gui/plugin_handler.py", line 102, in load
    self._load()
  File "/opt/ros/melodic/lib/python2.7/dist-packages/qt_gui/plugin_handler_direct.py", line 55, in _load
    self._plugin = self._plugin_provider.load(self._instance_id.plugin_id, self._context)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 72, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 72, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_gui_py/ros_py_plugin_provider.py", line 61, in load
    return super(RosPyPluginProvider, self).load(plugin_id, plugin_context)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/qt_gui/composite_plugin_provider.py", line 72, in load
    instance = plugin_provider.load(plugin_id, plugin_context)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_gui/ros_plugin_provider.py", line 106, in load
    return class_ref(plugin_context)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_reconfigure/param_plugin.py", line 51, in __init__
    self._plugin_widget = ParamWidget(context)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_reconfigure/param_widget.py", line 105, in __init__
    self, rp, self.sig_sysmsg
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_reconfigure/node_selector_widget.py", line 102, in __init__
    self._update_nodetree_pernode()
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_reconfigure/node_selector_widget.py", line 341, in _update_nodetree_pernode
    TreenodeQstdItem.NODE_FULLPATH
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_reconfigure/treenode_qstditem.py", line 94, in __init__
    self._set_param_name(grn_current_treenode)
  File "/opt/ros/melodic/lib/python2.7/dist-packages/rqt_reconfigure/treenode_qstditem.py", line 246, in _set_param_name
    self._toplevel_treenode_name = self._list_treenode_names[0]
IndexError: list index out of range

解决办法:

将/opt/ros/melodic/lib/python2.7/dist-packages/rqt_reconfigure/node_selector_widget.py文件中第325行改为if node_name_grn in self._nodeitems or node_name_grn == '':即可

解决rosdep init和rosdep update根本问题

ubuntu18.04安装melodic遇到的问题

针对目前安装ROS时出现的一些指令问题进行解析，主要卡在rosdep init和rosdep update这里，主要是被墙的太严重了。

下面开始解决它

sudo rosdep init
ERROR: cannot download default sources list from:
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list
Website may be down.

 在进行rosdep init的时候需要联网访问这个网址，然而这个网址无法进入，导致一直卡这报错过不去，目前网上有很多方法，我也都尝试了，可以参考一下

https://blog.csdn.net/u013468614/article/details/102917569

https://www.guyuehome.com/12640

https://zhuanlan.zhihu.com/p/43345574https://link.zhihu.com/?target=https%3A//www.cnblogs.com/liwe1004/p/11795932.htmlhttps://link.zhihu.com/?target=https%3A//blog.csdn.net/maolong2725/article/details/82530722

也可以找到一个文件，加一句话主要看运气，比较玄学，方法如下：

#打开hosts文件
sudo vim /etc/hosts
#在文件末尾添加
151.101.84.133  raw.githubusercontent.com
#保存后退出再尝试<br>或者添加<br>151.101.76.133 raw.githubusercontent.com

解决思路

在进行rosdep init 的时候访问raw.githubusercontent.com，这个其实就是github的用户数据服务器。rosdep 程序下载的就是github.com/ros/rosdistro这个包里的yaml文件。
因此得到一个思路就是：首先下载github.com/ros/rosdistro包，将下列文件里面的默认的进入raw.githubusercontent.com去下载文件的url地址全部改为本地的下载的包的地址。
解决过程

第一步

首先进入www.github.com/ros/rosdistro去把这个包下载下来

包名rosdistro-master应改为rosdistro

也可以从我的网盘下载

链接：https://pan.baidu.com/s/1B4E_spuSJ_E1MANxWVrLfw提取码：ja5d

第二步

修改这个包中rosdep/source.list.d/下的文件20-default.list，将这个文件中指向raw.githubusercontent.com的url地址全部修改为指向本地文件的地址（自己放置该包的地址），也就是该下载好的包的地址：以下是我修改好的样例：

# os-specific listings first
yaml file:///home/xxx/rosdistro/rosdep/osx-homebrew.yaml osx
 
# generic
yaml file:///home/xxx/rosdistro/rosdep/base.yaml
yaml file:///home/xxx/rosdistro/rosdep/python.yaml
yaml file:///home/xxx/rosdistro/rosdep/ruby.yaml
gbpdistro file:///home/xxx/rosdistro/releases/fuerte.yaml fuerte
 
# newer distributions (Groovy, Hydro, ...) must not be listed anymore, they are being fetched from the rosdistro index.yaml instead

***注意：***在py语言中：url本地文件地址格式是：file://+文件地址，后面更改其他文件中地址的时候也一样。

第三步

修改/usr/lib/python2.7/dist-packages/rosdep2/main.py中的默认的url的地址，但是经过代码阅读，该文件中并不存在指向raw.githubusercontent.com的代码。而且经过对代码的分析，提示报错的代码就在该文件中

def command_init(options):
    try:
        data = download_default_sources_list()
    except URLError as e:
        print('ERROR: cannot download default sources list from:\n%s\nWebsite may be down.' % (DEFAULT_SOURCES_LIST_URL))
        return 4
    except DownloadFailure as e:
        print('ERROR: cannot download default sources list from:\n%s\nWebsite may be down.' % (DEFAULT_SOURCES_LIST_URL))

由于其调用了download_default_sources_list()这个函数
而该函数就在/usr/lib/python2.7/dist-packages/rosdep2该文件夹下面的sources_list.py文件里面。而这个文件里面的代码则进行了访问raw.githubusercontent.com的操作，因此修改该默认url即可

# default file to download with 'init' command in order to bootstrap
# rosdep
DEFAULT_SOURCES_LIST_URL = 'file:///home/xxx/rosdistro/rosdep/sources.list.d/20-default.list'
 
# seconds to wait before aborting download of rosdep data

总结：该步实际并不是修改 main.py 文件里面默认url的指向地址，而是修改同文件夹下的sources_list.py文件里面的代码

第四步

修改以下两个文件里面的代码，修改方法类似：

/usr/lib/python2.7/dist-packages/rosdep2/rep3.py
/usr/lib/python2.7/dist-packages/rosdistro/__init__.py

下面是我分别修改后的样例：

修改rep3.py文件

/usr/lib/python2.7/dist-packages/rosdep2/rep3.py文件：

# location of targets file for processing gbpdistro files
REP3_TARGETS_URL = 'file:///home/xxx/rosdistro/releases/targets.yaml'
 
# seconds to wait before aborting download of gbpdistro data

修改__init__.py的文件

/usr/lib/python2.7/dist-packages/rosdistro/__init__.py的文件：

# index information
 
DEFAULT_INDEX_URL = 'file:///home/xxx/rosdistro/index-v4.yaml'
 
def get_index_url():

然后进行sudo rosdep init  就没有什么问题了

如果你是ubuntu20.04安装noetic的话，就要更改一些细节了：noetic不是更改/usr/lib/python2.7/dist-packages/了，而是更改/usr/lib/python3/dist-packages/

最后感谢原博主：

https://blog.csdn.net/nanianwochengshui/article/details/105702188