I have a client Server configuration with one connection, the server cannot process the requests received in parallel, it processes them in series, to overcome this problem, we developed a proxy server (installed between client and server) to receive request open connection with the server ==> send request server ==> send response to the client ==> close connection.
The problem we have is this, the response is sent divided on 2 part, we did a TCPDUMP on the port, we see that the request is sent devised on two part one with a length 1 and the second with à length 33
We don't know if it's a configuration on the server or on the network
Can some one help us ?
Related
I am working on a product which uses ZeroMQ (version 4.0.1).
The server and client communicate based on ZeroMQ ROUTER-socket.
To read socket events, server and client also create socket-monitor sockets (PAIR). There are three ports on which server binds and listens. Out of these three ports, one port is in a non-secured mode. Other two ports are using md5-authentication.
The issue I am facing is that, both the server and the client spontaneously receive socket disconnect for one of the secure port sockets (please see a log below). I have checked multiple times that server and client both have L3 reachability to each other.
What else I should check for?
What really triggers this error scenario?
zmq_print_callback:ZmQ: int zmq::stream_engine_t::read(void*, size_t):923
Stream engine recv():
TCP socket (187) to unknown:0 was disconnected
with error 107 [Transport endpoint is not connected]
Below sequence of events can trigger this error on server
Server receives ACCEPTED event for clientY and gets FD1.
Link-flap/network issue happens and clientY disconnects but server does not receive this disconnect.
Network recovers and clientY connects back to server.
Server receives ACCEPTED event for clientY and gets FD2. However, packets sent to this sockets does not go out of the server.
After 1 min or so, clientY receives "Transport endpoint is not connected error" for FD1.
Application can use this to treat as client disconnect.
There is delay seen on server machine while sending [SYN,ACK] packet to Client machine for the first connection attempt from client. These are some observations analyzed with sniffer tool wireshark:-
Due to this delay:-
Client application is sending the [TCP Retransmission] packet to server.
Later, connection timeout expires(3 seconds) on client side and it tries second connection attempt with server.
Surprisingly, server immediately sends [SYN,ACK] packet for second connection attempt to client back.
After sending [SYN,ACK] packet for second attempt, server responds back with [SYN,ACK] packet for the first attempt.
For better understanding, client application sends the connection request certain set server ports all together. Server sends [SYN,ACK] packet from the listening port which is one of these ports.
I will be pleased if somebody explains :-
Why there is delay in [SYN,ACK] packet from server machine?
Why server able to respond back immediately with [SYN,ACK] packet for second attempt but responded for first connection attempt after sending [SYN,ACK] for first attempt.
Who takes care of responding back [SYN,ACK] packet to client machine? Is it server application or any other operating system service?
The screenshot of wireshark is attached here. The above mentioned observation is on the basis of frame#20145 to Frame#20428
I have a client-server (Java) application using persistent TCP connections, but sometimes the Server receives java.io.IOException: Connection reset by peer exception when trying to write on the socket, however I don't see any error in the Client log.
This RST is probably caused by an intermediate proxy/router, but if that's the case, should this be seen on the client as well?
If the RST is sent by the client, it can be seen on it using a packet sniffer such as wireshark. However, it won't show up in any user-level sockets since it's sent by the OS as a response to various erroneous inputs (such as connection attempts to a closed port).
If the RST is sent by the network, then it's pretending to be the client to sever the connection. It can do so in one direction, or in both of them. In that case, the client might not see anything, except for a RST sent by the actual server when the client continues to send data to a connection it perceives as open, while the server sees it as closed.
Try capturing the traffic on both the server and the client, see where the resets are coming from.
I'm trying everything to NAT traversal to make a HTTP(or others) server be accessible from internet.
this is the previous question but with no luck.
HTTP Server behind NATs
So I'm trying to do the following
IE <--> agentC <---------NAT/Internet/.....----------->agentS<------->Apache Server
the scenario might be...
1.User input address in IE like "localhost:9999" (agentC)
2.agentC connect with agentS with Stun/TURN/ICE
3.agentS relay data to Apache Server and then reply to client.
I also refer to the following:
Is it possible to 'relay' a socket?
but the problem is:
1.the connection between agentC to agentS might be UDP, however the Http is on TCP, is it possible to "relay socket or packet"
2.I'm coding test code of agentS<---->Apache part,
((pp = popen("echo -e \"GET / HTTP/1.0\\n\\n\\n\"| nc localhost 80", "r")) == NULL)
.........
But the out put always "400 Bad Request".
(while type "echo -e "GET / HTTP/1.0\n\n\n"| nc localhost 80" in console will be successful)
3.I will modify a simple console chatroom to be agentS and agentC, is it possible to carry the http data (like pic,download...etc)?
Thank you for your patience
You don't really relay the socket, instead you relay the data. For example, "agentS" in your example opens a listening socket where it accepts connections from "agentC". When it gets a new connection from "agentC" then "agentS" connects to the web-server and enters a loop where where all it reads from either connection ("agentC" or web server) is sent to the other connection.
Since the two connections are independent it doesn't matter if one is TCP and the other UDP.
Also, if you need to do some processing on the data in "agentS" it's easy, as you actually have the data. The protocol between "agentC" and "agentS" doesn't even have to be HTTP, it can be whatever you want, as the programs can do protocol translation.
As a side note, when sending data to a web-server you end the lines with "\r\n", and the header is terminated by a single "\r\n" on its own line. So you only need to send "\r\n\r\n" after the GET request.
I have 2 sip clients on the same computer.
Both of them is registering to a server that is running on port 5060.
For the first client the UDP is on port 5060 and for the other is 5061. When I come from one client to another, after the ringing part i receive the error:
only one usage of each socket address is normally permited.
Got any ideas why I got this error?
Your server and client are both trying to use port 5060, hence the error message. Change the first client to use 5062 or something else.
Also, 5061 is normally used for secured SIP (normal listening port + 1 in the proxy/server). Do not use it for the second client.
It means you're clients are both trying to claim the same socket for the communication channel, or the server is trying to reclaim the socket given to client A, to reuse it for client B.
The software handeling the socket, should be smart enough to rely on the OS to assign port numbers instead of hardcoding the port numbers in the code, this is a 100% guarantee for socket issues.