I'm reading about how SSL works and tried to perform a handshaking with google pop3 server pop.gmail.com 995. I've found an example of the client hello message there. So, I connected to the gmail pop 3 server with
telnet pop.gmail.com 995
It's OK. Now I can send messages to the server. As far as I understand the first thing I need to do is to send is the client hello message. So I type the following line (I'll break lines after \r\n token for simplify reading):
ClientVersion 3,1\r\nClientRandom[32]\r\n
SessionID: None (new session)\r\n
Suggested Cipher Suites:\r\n
TLS_RSA_WITH_3DES_EDE_CBC_SHA\r\n
TLS_RSA_WITH_DES_CBC_SHA\r\n
Suggested Compression Algorithm: NONE
Press Enter and receive the message
Connection closed by foreign host.
What's wrong? I was supposed to receive a server hello message? What do I send to receive that?
No, this is not possible. The text you're trying to type in is a human-readable representation of a ClientHello message, not the real thing. The real ClientHello message is binary data, and cannot be entered through a Telnet session.
You can use this command. After connect put your request like using telnet.
openssl s_client -connect pop.gmail.com:995
Related
I write a simple server application. In that application, I created a server socket and put it into the listen state with listen call.
After that, I did not write any code to accept the incoming connection request. I simply waited for the termination with pause call.
I want to figure out practically that how many bytes are buffered in the server side if the connection is not accepted. Then I want to validate the number with the theory of the TCP.
To do that,
First, I started my server application.
Then I used "dd" and "netcat" to send the data from client to server. Here is the command:
$> dd if=/dev/zero count=1 bs=100000 | nc 127.0.0.1 45001
Then I opened wireshark and wait for the zero-window message.
From the last properly acknowledged tcp frame. the client side can successfully send 64559 byte data to the server.
Then I execute the above dd-netcat command to create another client and send data again.
In this case, I got the following wireshark output:
From the last successfully acknowledged tcp frame, I understand that the client application can successfully sent 72677 bytes to the server.
So, it seems that the size of the related buffer can change in runtime. Or, I misinterpret the output of the wireshark.
How can I understand the size of the related receive buffer? What is the correct name to refer that receive buffer in terminology? How can I show the default size of the related receive buffer?
Note that the port number of the tcp server is "45001".
Thank you!
Hey i have a quick question about some ssl stuff.
Is there any way NOT to send acknowledgement (ACK) back to the server after its response?
What am i doing, is testing a friends webapp, written in PHP i suppose, but i don't have a source code, and i think this is more of a general thing. What am i doing is asking a server for some data, handshake happens, i receive data and send ACK that the data were recieved. Then the server "FIN" the connection.. Thats what usually happens, but i'm using Burp proxy to intercept the servers response and noticed that if i drop the response the connection state is on "CLOSE_WAIT" and i don't receive the FIN signal after that, but the server know that i received the data.
So is there any way not to tell the server that i received the data? Basically fake that the data were lost somewhere, but still look at the response? Can Burp Suite do something similar to this or do you know any handy tools that might help? I can provide more info you want.
Thanks a lot!<3
I am using Spring Integration 2.0.3 with TCP. Application behavior is, it is acting as the TCP client and sending a message to the third-party tool using TCP. So application makes the connection to a third party tool using TCP, sends the message, waits for the reply and when that is received (again acting as the client) will close the connection. Now the issue is third-party tool can neither add any terminator nor make fixed length message.
As per my understanding, there are three ways to make a packet and send it to application
1)Always send fixed-sized messages
2)Send the message size with each message
3)Use a marker system to separate messages
But I cannot use any way mentioned above, I want to know how my application can receive the response message in this scenario, Is it possible?
Is your program supposed to close the connection once you have received the message? Or is the other program supposed to close the connection once it has sent the message to you?
If the latter then it's no problem since you just read until the connection is closed.
If the former, and you can't alter the application protocol and it doesn't already specify these things (is there a specification anywhere?), then wait with a timeout. If you haven't received anything within X seconds consider the full message received and close the connection.
My device and socket communicate through TCP. Now i want to load test my server so i try to use JMeter.
Server and device keep the connection alive. I will need to send login message before sending any other message. And each message doesn't have any end line character but using some bit to define how long that message is.
Now when i send out my login message, server response with success code. Because the connection is keep, and there no end line character, JMeter doesn't know when will it get full response, so it wait until timeout. I even try Response assertion, using contain word but still not working.
My question is what should i do for this case so when JMeter receive some bit, for example 'SUCCESS' word from server, JMeter will understand that it already pass and keep the connection for next request.
within a small embedded application I'm providing a Telnet server for sending simple commands to it. For testing I connect to it using putty. Now I found there are 21 bytes of some data are sent to the server on connection. So...what could this be? Is it a initialisation sequence?
From my understanding telnet is a plain connection which should not have such data...
Thanks!
OK, I got it: when selecting "Active auto negotiation mode" in Putty it sends these data with additional information of whatever...so one has tod rop all characters with an ASCII code larger than 127 to ignore these data.