All Questions
50
questions
3
votes
3
answers
1k
views
How does HTTP Keepalive handle multiple requests along with EOF from same origin?
says a client has multiple files to post to a server via HTTP Post method, there will be two api calls. since I don't want to create two TCP connections and I want to reuse TCP connection, so I use ...
- 135
0
votes
1
answer
245
views
How is an IP address assigned to a process in TCP?
When TCP connection is established between two sockets, suppose that there are multiple NICs in the computer, so which IP address will the socket bind [ or - which IP address will be passes into bind()...
- 11
0
votes
1
answer
1k
views
Meaning of IPTABLE duplicate values
I'm new to IPTABLES and when I execute the following command
/sbin/iptables --list -n | grep 16381
I could see multiple entries as shown below :
ACCEPT tcp -- a.b.c.d 0.0.0.0/0 ...
0
votes
1
answer
541
views
How can I identity which process is sending data to a certain host on Linux?
As per title, I want to figure out the process responsible for certain traffic. I can see the traffic in wireshark, but I don't know which process it is.
Is there any straightforward way to do it? I'm ...
-2
votes
1
answer
239
views
How to investigate why a computer stops a TCP connection?
I've just written this question on another StackExchange site, but I was advised to ask the same question here.
I would like to broaden the question: how can I know why a host closes a TCP socket ...
- 2,283
0
votes
1
answer
745
views
Address of a Transport layer?
In TCP/IP protocol stack following protocol level addresses exists:
Data Link layer - MAC address
Network layer - IP address
Transport layer - ?
Application layer - Socket address which is ...
- 45
1
vote
0
answers
52
views
TCP server device for USB access readers
I have a BarCode reader that spits out data over a Virtual COM port (RS232 Serial) through a USB cable. I have a server running and managing a facility, and I need to read data coming off the BarCode ...
- 11
0
votes
3
answers
587
views
Connect a socket to another PC in same NAT
Hey I've got two machines on the same network. They get their IP info back from an external webserver. Same IP due to NAT but different ports locally. Hmm that's weird.. they can't socket up or even ...
- 11
2
votes
0
answers
2k
views
WebSocket connections originating from local network all use same client-side port (instead of ephemeral) when connecting to local webserver - Why?
I set up a webserver on a virtual machine on my home desktop. I have my router forward several ports (80, 443, etc) to my desktop, when then forwards them via NAT to the virtual machine (see diagram ...
- 21
0
votes
1
answer
4k
views
Increase buffer size for a specific socket on Linux
I am using CentOS7 and I have to increase the send buffer size (SO_SNDBUF) on a socket listening on a specific port. The application that has the port opened does not natively support this.
Few things ...
1
vote
0
answers
45
views
understand ss -to4 output for a jdbc connection
My application connects to a database over JDBC, and performs a lot of sequential inserts. There is only 1 JDBC connection opened by the application. As the performance is not as expected, I started ...
- 11
4
votes
1
answer
5k
views
How can I know what is preventing my socket to bind to localhost:50060-50959
I am using this Python code to listen to a port on my Windows 10 system:
import socket
for port in (50059, 50060, 50959, 50960):
try:
print(socket.socket(socket.AF_INET, socket.SOCK_STREAM)....
- 1,728
2
votes
0
answers
307
views
How can I use the "location of socket in memory" field in /proc/net/tcp
I'm working on a proxy for linux(C++) that, amongst other functions, keeps track of tcp connections and associates them with the process's pid. To do that, I get the inode in /proc/net/tcp and then ...
1
vote
1
answer
1k
views
Checking Nagle Algorithm on opened socket
One of the platforms we use opens TCP sockets (No source code available).
I need to check if the Nagle Algorithm is disabled or enabled on those sockets.
The operating system used can be Windows or ...
0
votes
0
answers
385
views
Why is my TCP connection attempt via PHP acting weird?
I'm not sure if this is better here or on SO but since the issue isn't in the programming I figured it applies here (or on U&L or on serverfault, but I guess/hope I'm fine on here).
I want to ...
- 2,505
2
votes
0
answers
1k
views
Need help figuring out a random connection timeout issue on a server
I discovered this issue trying to loadtest a custom node.js websocket server, where some sockets are failing to connect (they hit the connection timeout). It does not appear to be related to the ...
- 121
1
vote
1
answer
1k
views
sudo netstat -antp not showing PID
i am testing stuff with sockets and i encountered that strange case :
i coded i very simple tcp server in c, i made it block after accept(), just to see what happen when accepting multiple connection ...
0
votes
1
answer
1k
views
How to make a port listener code in the server that hosts my website?
I have my website hosted in godaddy, and I want to test one of the Embedded Application's TCP data transfer using the IP and port number of my website, for this can I use any php script (something ...
0
votes
1
answer
883
views
Running Process Monitor causes application to work
This is a longshot, but perhaps someone with knowledge of the internal workings of Sysinternal's Process Monitor may have an idea.
Recently we've had a very murky problem at work. We have a software (...
- 115
1
vote
0
answers
211
views
Firewall : Is inbound required for getting response while Outbound rule already there?
I developed one MVC web application which have Web APIs and hosted in Amazon Instance and one windows application for calling those APIs for getting response from that server.
Both Web and Windows ...
0
votes
1
answer
2k
views
TCP socket buffer for every flow
Does the linux kernel create a buffer for every TCP connection, for example when we have 1000 tcp connections the kernel creates 1000 socket buffer and stores the packets of individual flow on its ...
- 11
1
vote
1
answer
6k
views
Socat not closing tcp connection
I use socat 1.7.3.1-r0 and run following command on an alpine 3.3 linux server:
socat -d -d -d PTY,link=/dev/ttyFOOBAR,echo=0,raw,unlink-close=0 TCP-LISTEN:7000,forever,reuseaddr
Socat will listen ...
- 145
2
votes
2
answers
5k
views
RST sequence number and window size
RFC793 states the following about RST processing:
In all states except SYN-SENT, all reset (RST) segments are validated
by checking their SEQ-fields. A reset is valid if its sequence number
is ...
- 21
3
votes
1
answer
1k
views
Is it necessary for an RST packet to have an acknowledgement number?
I am studying about TCP reset attack. I know that some RST packets have an acknowledgement number (with the ACK bit set), and some RST packets do not have an acknowledgement number (the ...
- 31
1
vote
1
answer
532
views
Acknowledgement number of an RST packet
This question states that the acknowledgement number of an RST packet should be 0, but I have found it to be other than 0 when I captured some HTTP packets using Wireshark.
So when does the ...
- 13
5
votes
1
answer
3k
views
How to list socket options of running processes?
Is there a convenient way (e.g. a readily-available command or a program that I can write using standard system calls) to list socket options (e.g. TCP_NODELAY) of an open TCP socket of some running ...
- 463
0
votes
1
answer
3k
views
TCP socket to serial port
Is is possibile to remotely access a serial port by tcp socket server? Exists this kind of software?
It is the opposit of this question:
Any free application to redirect serial communication to TCP/IP?...
- 2,311
0
votes
1
answer
91
views
TCP socket communication from client to server
I am trying to test the performance of a client/server application that uses TCP communication.
If I trigger multiple requests from the client, would it flow through the same connection/pipe to the ...
- 3
1
vote
0
answers
27
views
Route only on output chain?
I have two machines A and B. I want to send iperf traffic from A to B, but first have it route through a userspace program on A. I did this with a tunneling device: therefore, I used the command ip ...
- 111
5
votes
2
answers
6k
views
Data retransmission and WSAECONNABORTED (10053) socket error
Say I have two sockets that are connected to each other (Socket A and Socket B).
If the computer that have Socket B is unplugged from power, then if Socket A tries to send some data to Socket B, the ...
- 51
3
votes
2
answers
2k
views
Are FIN packets guaranteed to arrive?
In the 4-way handshake, we have the following:
FIN ------->
<------- ACK
<---x--- FIN (what if this packet is lost?)
ACK ------->
What happens if the third packet is lost, will it be re-...
- 31
0
votes
1
answer
2k
views
List all open sockets in /dev/tcp/localhost/
Is it possible to list all open sockets in /dev/tcp/localhost/ on a Linux machine?
I want to list all sockets where the following command would return 0:
timeout 2 bash -c "cat < /dev/null > /...
- 127
0
votes
0
answers
16
views
What happens when I terminate a process and the socket send buffer is not empty? [duplicate]
In Windows (and probably in other operating systems), if a process has a TCP connection with another process on another machine, and then I terminate the process, an RST packet will be sent to the ...
user4579580
4
votes
1
answer
929
views
What happens when I terminate a process and the socket send buffer is not empty?
In Windows (and probably in other operating systems), if a process has a TCP connection with another process on another machine, and then I terminate the process, an RST packet will be sent to the ...
- 41
0
votes
3
answers
1k
views
What happens when 2 hosts simultaneous establish a connection in a 3-way handshake
Say two hosts, A and B, both attempt to start a connection with each other, but the SYN from A gets to B before B's SYN arrives at A.
My answer is that A would sent SYN ACK and would ignore the SYN ...
- 900
3
votes
1
answer
3k
views
Does an open TCP socket connection consume data when not used?
I have a TCP socket connection established between my server and a modem which has a active GSM module and sim card installed.
I create this wirless 3G connection via socat:
/usr/bin/socat open:/dev/...
- 145
1
vote
1
answer
1k
views
Linux Kernel TCP socket functions
So I have been looking through the Linux Kernel v3.8.0-19-generic source code and I noticed that the proto struct, whose members are virtual functions for socket operations depending on the particular ...
- 215
3
votes
1
answer
6k
views
SYN-ACK not received
On a standard TCP connection between server and client, I have this issue: the SYN-ACK is not received from the client, while it is sent from the server. I could see this on Wireshark from both server ...
- 131
1
vote
1
answer
166
views
Why is it possible to continue working in a ssh session after a network disruption?
What enables the Secure Shell client and server to resume communication after one or several network interfaces in the communication path between them is shut down and re-appears some moments later? ...
- 11.4k
2
votes
1
answer
4k
views
How to Maintain an Inactive Tcp Connection?
If a TCP server establishes a TCP connection with a TCP client and the TCP client never sends any packet to the server.
I roughly know firewalls near the TCP server may send an RST to it. Or there is ...
- 3,055
1
vote
1
answer
654
views
TCP vs UDP Error-Checking
I've bounced upon two articles that describe in-depth on how TCP and UDP connections work. However there is some kind of inconsistency. Where one article tells me that UDP does no Error-Checking at ...
4
votes
2
answers
18k
views
TCP: Maximum number of connections (client and server)
In the description of TCP in the Wikipedia, it is stated that
The number of sessions in the server side is limited only by memory and can grow as new connections arrive, but the client must ...
- 1,311
1
vote
1
answer
1k
views
ARP: 'Who has' broadcast resulting in TCP segment losses
I have an issue with a simple TCP connection between two PCs (both Windows XP SP3) connected by direct wire to each other. These PCs have IP address 10.10.10.1 (server) and 10.10.10.2 on the network ...
- 83
5
votes
1
answer
1k
views
Does TCP/UDP send file sequentially or randomnly?
Does TCP/UDP protocol always send or receive file packets sequentially? Would it possible to make a choice which data packets will be sent first using sockets API?
- 53
1
vote
1
answer
1k
views
Sending a file via TCP/UDP socket
I'm reading about TCP and UDP from a article. In the end what I understood is that UDP is faster than TCP but it is unreliable. So if I'm going to a send a file, If use UDP, would it
be faster than ...
- 13
3
votes
4
answers
143
views
TCP/IP on the transport level
I'm trying to understand what happens when I send a packet using a socket on the transport level. Do all packets which leave my computer go first to a geographical location designated by my ISP? Then ...
- 143
0
votes
1
answer
310
views
Video player that can be controlled by Socket / TCP
Is there a Video Player that can be controlled with TCP?
I think VLC supports this - but I can't find any easy to follow instructions on how to do this.
I will be using this on a windows 7 machine, ...
- 223
2
votes
1
answer
409
views
How does the Inetutils telnet utility determine if a connection is still alive?
I've started using sockets in programming with Java (I have experience with Python), and while testing a server that I'd written with the telnet command, I noticed that the utility responds ...
- 168
3
votes
3
answers
242
views
Distinct Proxying for any TCP-related Protocol
I'm not sure what to call it (proxy/redirection/relay), and I am hoping some software or solution possibly exists for linux.
My intention is to be able to listen on a single public facing ip:port (...
- 688
0
votes
2
answers
256
views
is there a single-end available bandwidth measurement tool
i am doing my graduation thesis,currently i need a tool that is capable of measuring the
available bandwidth between client and servers.i have googled that, the link
http://www.icir.org/models/tools....
- 101