Need help RCon Packets Socket Bash


 
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# 1  
Old 10-04-2018
Need help RCon Packets Socket Bash

Hi and thank you in advance for taking the time to help. As I have less than 5 posts it said I had to remove the links you will need to help so good luck!

I am having issues building a packet and sending it to a Minecraft RCon server.

This is the Minecraft RCon Protocol information can be found here (link removed)
It is an implementation of the source RCon protocol (link removed)
The basis of my code is (link removed)
The completed code of that linux question can be found here (link removed)

My modifications so far are listed below, I know its not elegant but then im working with someone elses code style and really just experimenting to see what works. So far I can tell that a socket is being created but cant figure out how to build a packet of the format required and cant tell if anything is being set at all.

1. The documentation say's that the packet components are 32bit littleendian integers, I have no idea how to do that. I think because im on linux they are littleendian but how do I make them 32bit.

2. The payload must be byte[] form, I am not sure how to do that either.
3. Still also trying to find a way to get a response from the server.

My experimenting so far:

Code:
#!/bin/bash
# configuration
HOST=""
PORT=
PASSWORD=""
REQUESTID=$RANDOM
COMMAND="$1 $2 $3 $4 $5"


# define functions
socksend ()
{

    REQUESTID="1"
    TYPE="$2"
    PAYLOAD="$PAYLOAD"
    
    echo "Host: $HOST"
    echo "Port: $PORT"
    echo "sending: $PAYLOAD"
    #echo -ne "$SENDME" >&5 &
    DATA=$REQUESTID
    #+$TYPE+$PAYLOAD
    #LANG=C LC_ALL=C  # Googled this. Not sure how this line works but was intended to make length in bytes. Redundant now.
    LENGTH=`echo -n $DATA | wc -m`
    #${#DATA}
    #LANG=$oLang LC_ALL=$oLcAll # Googled this. Not sure how this line works but was intended to make length in bytes. Redundant now.
    echo "Length: $LENGTH"
    printf '$LENGTH$DATA%s\0%s\0' >&5 &
}

sockread ()
{
    LENGTH="$1"
    RETURN=`dd bs=$1 count=1 <&5`
}
#2> /dev/null
echo "trying to open socket"
# try to connect
if ! exec 5<> /dev/tcp/$HOST/$PORT; then
  echo "`basename $0`: unable to connect to $HOST:$PORT"
  exit 1
fi
echo "socket is open"

# send login request
TYPE=3
PAYLOAD="$PASSWORD"
echo "Payload: $PAYLOAD"
socksend $REQUESTID $TYPE $PAYLOAD

# read 7 bytes for "success"
sockread 1
echo "RETURN: $RETURN"

echo "sending part 2"
TYPE=2
PAYLOAD="$COMMAND"
echo "Payload: $PAYLOAD"
socksend $REQUESTID $TYPE $PAYLOAD

# read 7 bytes for "success"
sockread 1
echo "RETURN: $RETURN"

Output so far:
Code:
trying to open socket 
socket is open 
Payload: ######### 
Host: #.#.#.# 
Port: ##### 
sending: ######## 
Length: 1 0+0 
records in 0+0 
records out 0 
bytes copied, 0.00115984 s, 0.0 kB/s 
RETURN:

 sending part 2 
Payload: time set night 
Host: #.#.#.# 
Port: ##### 
sending: time set night
 Length: 1 0+0 
records in 0+0 
records out 0 
bytes copied, 2.9759e-05 s, 0.0 kB/s 
RETURN:

There are probably a lot of things im doing wrong but I don't work with binary much. Bash was chosen as its the easiest for me to interface with other sources. Would like to keep this as simple as possible so the staff of my community will have a chance of being able to understand and use it to some degree. I will rewrite this in my own code style later but for now im just wanting to get it working.




Moderator's Comments:
Mod Comment Please use CODE tags (for data as well) as required by forum rules!

Last edited by Neo; 10-15-2018 at 12:48 AM..
# 2  
Old 10-05-2018
BASH is exactly the wrong language and tool for binary communication over network sockets.

Probably the best thing for you to do would be to install the mrcon tool rather than rolling your own. mcrcon download | SourceForge.net
# 3  
Old 10-15-2018
Got it working!
# 4  
Old 10-15-2018
Quote:
Originally Posted by Stuperfied
Got it working!
Many thanks for not telling us how you did it. This way we have all learned so much.

bakunin
# 5  
Old 10-17-2018
From small amount of view and replies I didn't think anyone was particularly interested. The views seem to have gone up a lot though so here it is.



I echoed to a variable but appended nulls and hex encoded to preserve them. Had to also trim the white space from the end but it worked. Could just have easily used printf and inserted nulls using flags but I got this working and it was good enough.
# 6  
Old 10-17-2018
We didn't have much information from you on what you wanted, which made replying difficult. We still don't know exactly what you wanted, or what exactly you did.
# 7  
Old 10-21-2018
Let me try and help. Unfortunately I was not sure what I was doing wrong and so did not have specific questions to ask. I have highlighted the key indicators in the text, hopefully that will shed some light on it.


Quote:
I am having issues building a packet and sending it to a Minecraft RCon server.
Now this first line tends to suggest that this is the area I need help with. If we break it down into its components, it could give us an idea of what im trying to do. A quick google of those topic areas could shed some more light.



and then when you mix it with these...
Quote:
1. The documentation say's that the packet components are 32bit littleendian integers, I have no idea how to do that. I think because im on linux they are littleendian but how do I make them 32bit.
Ok, so breaking this part down tends to suggest that there is documentation on the topic in question which is a good thing. This means we can google it and get more relevant information. It also looks like im having issues converting the packets to 32bit form, perhaps something you could help me with. A quick read of my code below may indicate where im going wrong and then you could make some suggestions.



Quote:
2. The payload must be byte[] form, I am not sure how to do that either.
Another clue, this looks like a simple one as the payload is probably a part of the packet and is most likely stored in a variable. We can examine the code below to make sure and then maybe provide some helpful insights.


3. Still also trying to find a way to get a response from the server.[/QUOTE]
Not really very helpful as the server probably wouldn't respond if im sending bad data to it but a quick look at my code might reveal if im doing any thing wrong.



Admittedly, it would have been better if I actually added some links as reference so you could know what I was on about. Which is probably why I added this line.
Quote:
As I have less than 5 posts it said I had to remove the links you will need to help so good luck!
Next time I will try to ask more specific questions like on stackexchange to make it easier for you. Oh wait, was that another clue...
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