23,775 questions
0
votes
0
answers
14
views
Kubernetes: Long-lived TCP connections dropping through kube-proxy / Service LoadBalancer. Direct node connection better?
I’m building a service that needs to maintain a very large number of long-lived TCP connections (persistent sockets). Low latency and stability are essential.
We’re running on a managed Kubernetes ...
- 382
1
vote
1
answer
103
views
Cant open more than 8000 tcp connections with Java
I am trying to open to open 10K+ connections to a server, but my app stops at 8K connections when looking at the server logs. When using two remote servers it will struggles when reaching between 8K ...
- 11
0
votes
0
answers
61
views
Socket TCP connection through Radmin (can't connect) in Console Application
I made a simple console messenger to test the possibility of connecting 2 or more computers for my game using RadminVpn+Sockets but its not working. I can connect to myself using my radmin ip but if I ...
- 9
2
votes
1
answer
125
views
Received request message is changed from TCP server after upgrading Spring boot to 3.4.2
After upgrading Spring Boot from 2.7 to 3.4, receiving message from TCP server to our service is getting changed with different code. For example, previously the received message is 1784 after ...
0
votes
0
answers
100
views
Unsubscribe from topic not working when using persistent session Mqtt
I have a Qt application that uses the qtmqtt module to implement a simple MQTT setup.
I’m running two instances — one as a subscriber and one as a publisher.
In the app, users can right-click on any ...
- 1,334
0
votes
1
answer
107
views
MQTT subscriber doesn’t receive queued messages when publisher uses QoS 0?
I’ve been reading the MQTT documentation, and as I understand it, there are two types of Quality of Service (QoS) levels involved:
Publisher QoS: determines the delivery guarantee between the ...
- 1,334
-1
votes
1
answer
80
views
Seastar: per-shard TCP listeners not binding or exiting silently on non-0 shards
I’m trying to start a per-shard TCP listener in Seastar, where each shard binds to its own port (6010 + shard_id). On shard 0, everything works — the listener binds and accepts connections fine. But ...
0
votes
0
answers
56
views
MQL5 SocketConnect fails with error 4014 connecting to local TCP server
I’m developing an MQL5 Expert Advisor that should connect to a local TCP server (127.0.0.1:5001).
The server is running and responds correctly to Telnet.
In MetaTrader, I added 127.0.0.1:5001 in ...
-4
votes
1
answer
52
views
Can we attach a ebpf program after tcp reordering? What mechanism should we use any ready examples folks?
Can we attach a ebpf program after tcp reordering? What mechanism should we use any ready examples folks?
We tried at tc level but see problems of packets not being ordered/assembled as expected!
...
1
vote
1
answer
81
views
Why does the NetworkStream.ReadAsync call end the loop
I have a Task that should continuously read from a Tcp stream and place the data into a ConcurrentQueue for processing. Stepping through the function I notice that the ReadAsync Call does not return.
...
- 143
0
votes
0
answers
71
views
Run Pyshark on TCP Port interface?
In order to get the data I need from Tshark I run with the flags:
tshark -i [email protected]:11111 -T ek
and we are streaming data to the TCP port 11111.
I'm trying to recreate this with pyshark:
...
1
vote
2
answers
148
views
TCP Connection Refused Given multiple concurrent connection
I try to play with multiple concurrent tcp connection in Java.
Given 250 concurrent tcp connection, some of them will get connection refused.
It surprises me due to only 250 connection.
In large web ...
- 871
0
votes
1
answer
113
views
How can I handle multiple TCP clients concurrently in Node.js without blocking others?
I'm trying to build a lightweight TCP server in Node.js that can handle multiple clients concurrently without blocking any of them — and all of this in a single-threaded manner, staying true to Node....
0
votes
1
answer
138
views
How can I create tcp client for simple chat system in .NET?
I am trying to create a chat system using tcp. I have 3 apps, 1 tcp listener and 2 tcp clients. I want to create a simple chatting system but I can't figure it out.
I have created a server that ...
- 15
0
votes
1
answer
65
views
System (PID 4) listens on my port after I close the listening socket
On Windows Server 2022 I'm running a custom HTTPS server (part of a larger app). The service binds, listens and then accepts on port 81 for a while and netstat -abn shows:
TCP 0.0.0.0:81 ...
- 4,707
0
votes
3
answers
115
views
Why is HTTP CONNECT safe to open an SSL tunnel through a proxy
As I understand, in order to open a SSL tunnel between client and a server through a proxy:
we open a TCP socket with the proxy.
we make an HTTP CONNECT method, which basically makes the proxy only ...
- 403
1
vote
2
answers
103
views
TCPListener returns error when it disconnects
When the TCP client disconnects, the TCP listener is giving an error;
2 clients just send random messages every second. When I close one client, the listener is giving an error and because of that the ...
- 15
2
votes
0
answers
104
views
TLS 1.3 unexpected server socket close connection
i have the following code which works correctly in TLS 1.2 but fails in TLS 1.3 (in windows platform, linux this doesn't happen, in fact if you place the server end on windows, and client on linux it ...
- 51
0
votes
0
answers
172
views
How should I handle the proxy protocol in a Fastify server?
Nginx config:
stream {
map $ssl_preread_server_name $backend_upstream {
api.xxx.com backend_1;
}
upstream backend_1 {
server 127.0.0.1:4433;
}
server {
...
- 1
2
votes
1
answer
114
views
Cannot set TCP_MAXSEG in macos
I was writing a simple C server and experimenting with setsockopt, so I wrote the following:
int lsock = socket(AF_INET, SOCK_STREAM, 0);
int mss = 576;
if (setsockopt(lsock, IPPROTO_TCP, TCP_MAXSEG, ...
- 57
-1
votes
1
answer
71
views
How to handle a fragmented UDS/UDP message? [closed]
I'm building a high velocity distributed database in Rust, using io_uring, eBPF and the NVMe API, which means I cannot use 99% of the existing libraries/frameworks out there, but instead I need to ...
- 2,578
1
vote
1
answer
80
views
Can a HTTP response get lost without the server noticing?
I'm designing a REST-Webservice and pondering the following scenario:
Client calls the endpoint (e.g. HTTP POST /something)
Server (synchronously) handles the request, responds to client (e.g. with ...
0
votes
0
answers
67
views
RabbitMQ block ports
unfortunately, after connecting RabbitMQ, I can't open my app on any port. After running, my app is up, but while RabbitMQ is running in Docker, I can't open Swagger on localhost with any port that I ...
- 21
0
votes
2
answers
88
views
Prevent reading data from a closed TCP socket
In my application, a client and a server communicate over a TCP socket using a request-reply protocol. Sometimes, because of network issues or application issues, the socket read on the server side is ...
- 41
3
votes
2
answers
88
views
Javafx MediaPlayer to play partially downloaded Media file (TCP/UDP, not HTTP)
Javafx MediaPlayer class plays files loaded into a Media object. The Media object can load local Media files or via HTTP.
My Client-Server uses TCP/UDP, not HTTP. I assume that media files need to be ...
- 121
1
vote
1
answer
138
views
Get open TCP/IP socket count on ESP32 / ESP-IDF
How can I get the number of currently open / active TCP/IP connections on the ESP32 IDF platform?
- 11.4k
1
vote
1
answer
80
views
How to design an embedded code that can handle three types of connections: MQTT, TCP sync and TCP async? Fail considerations
Our system is running on FreeRTOS. The server sends our device operation requests (via MQTT, TCP sync, TCP aysnc) and some operations have different number of steps/states.
Scenario 1:
Server ...
- 577
-4
votes
2
answers
187
views
How to send a raw TCP packet over IPv6 using Scapy?
I am trying to send a raw tcp packet over Ipv6 using Scapy. But I always get the warning: No route found for IPv6 destination (ipv6 address) (no default route?)
I am deploying in Kali Linux.
My ...
- 17
0
votes
0
answers
44
views
Connection lose with the device when i try to receive data from GT06 gps tracker
This is the debug shows when i run my script
2025-05-16 13:39:06,951 [INFO] [('106.209.213.128', 61576)] New connection
2025-05-16 13:39:06,991 [INFO] [('106.209.213.128', 61576)] Login: ...
0
votes
1
answer
77
views
getpeername - getting the final (actual) TCP server port the client connects to [duplicate]
I have successfully created a client/server TCP encrypted proxy server in C, all from scratch. As part of generating a unique IV for each connection, I am using the current time and the client's ...
- 11
0
votes
0
answers
51
views
Python http.server requests gets reset (RST) connection after every request using curl when trying to run HTTPS server
With Curl I get the data correcty, but after connection:
command:
curl https://172.17.0.1:8443
Result:
<html>
<data>....</data>
...
curl: (56) OpenSSL SSL_read: error:0A000126:SSL ...
- 1
0
votes
0
answers
18
views
Jenkins not accessible on EC2 RHEL instance
I have an instance EC2 installed with Jenkins but it’s not accessible. I have investigated almost everything within my understanding but seems i need more help to check this further.
Can someone ...
0
votes
1
answer
49
views
Can HTTP do chunked transfer while the page is gzipped
I'm working with embedded devices (STM32), the device would have a TCP server (HTTP server). The internal memory and flash is limited, so a more complex page wouldn't fit to the device. I would need ...
- 70
0
votes
0
answers
60
views
What will happen if I send 2 SYN packets to the server together with same 4 tuple but different sequence number?
The SYN packets are sent together before receiving any SYN-ACK from the server. Both SYN has the same source dest IP address & port. They only differ in seq no, so what will happen in this case?
0
votes
1
answer
105
views
Handcrafted TCP SYN packet yields no response
I have this code where I'm manually crafting TCP SYN packets in C by setting all IP and TCP header fields myself, including the TCP flags and checksum. When I send these SYN packets to an open port on ...
- 17
1
vote
1
answer
74
views
ZMQ Dynamic Discovery with XPub-XSub
I'm attempting to implement dynamic discovery of networked "nodes" using ZMQ's XPub-XSub pattern. Every example I can find online is limited to a single machine - using localhost for the IP ...
0
votes
0
answers
76
views
how to process ordered TCP packets concurrently in Go without blocking?
I'm developing a client that will receive packets from a server. Basically, I just need to guarantee the order of receipt, but I'm having a small problem with making the processing of these received ...
- 1,652
1
vote
0
answers
76
views
How to setup modem iRZ MC55iT | GPRS | Connection between PR200 and server
I have:
PC-server (Windows 10) with Java program
OWEN PR200 (ПР200, programmable relay)
GSM modem iRZ MC55iT
PC-client with installed Owen OPC Server and Scada
I need to make a two-side ...
- 21
0
votes
3
answers
124
views
Corrupted files with TCP process - How to ensure the transfer?
I'm facing an issue with MP4 file transfers over TCP.
I’m trying to send MP4 files from a Raspberry Pi with a camera to another Raspberry Pi with an SSD connected for storage.
According to online ...
- 1
0
votes
1
answer
84
views
Handling Early TCP Data and Registration Races in Spring Boot Behind an NLB in Kubernetes
I'm experiencing an issue with how my Spring Boot application (using Spring Integration) handles TCP connections in a Kubernetes environment. My setup includes an NLB (Network Load Balancer) in front ...
1
vote
0
answers
40
views
TCP Conncection wait for the respons in Flutter
Future<String?> sendAndReceiveCommand(String value) async {
try {
final ipParts =
'192.168.4.1'.split('.').map((part) => int.parse(part)).toList();
final ipAddress =
...
- 79
1
vote
1
answer
78
views
Make Connection Not Reset When STA Connects To a New Network
I am making a device that requires web interface and this is how I setup WiFi (inspired by my smart plug):
open AP for devices to connect
make itself's 6.6.6.6 so clients can send request to that IP
...
- 25
0
votes
0
answers
35
views
Database pool connections not visible using lsof under no load
I'm working on a project which involves NodeJS, and using Typeorm to create a connection to a database. The Typeorm library utilizes a connection pool in order to create ten connections to a database ...
- 73
0
votes
2
answers
62
views
socket.recv() response varies in length
I have a normal TCP client connection which I use to retrieve data from a climate sensor (SCD30). In theory, it does what it is supposed to do, but I always get different numbers of bytes.
with socket....
- 15
2
votes
1
answer
48
views
How to set KEEP_ALIVE parameters via C code
I have a Client-Server set up in C. The Client is running on a development board (FreeRTOS with lwip stack). Server is running on a Ubuntu. I am trying to set the KEEP_ALIVE params using the ...
- 21
0
votes
1
answer
241
views
How do I include STX (Start of Text) and ETX (End of Text) characters as prefixes and suffixes to TCP Sampler in JMeter
I'm sending a text to server which a Socket message connected via a Port and IP
I've used JSR223sampler to check the connection, which says "Connected"
This is my Text message
PLPL|WM|SL|AS|...
- 429
1
vote
0
answers
36
views
should we consider application layer message size
When application layer work upon TCP, do we need to consider the application message size if we want to get better performence? As PMTU is most likely unavaliable, if we choose a size as 3000 which is ...
- 11
0
votes
0
answers
57
views
300ms delay in network, kernel's TCP write buffer filled to the brim in embedded linux
I'm writing a semi-realtime application for an embedded board running BusyBox which packages and sends some telemetry data (around 100KB) on a TCP socket every 100 milliseconds. This board uses the ...
- 23
0
votes
0
answers
51
views
TCP packet TSval, TSecr
My application is creating a connection to Redis and using redis to store key/value. I am using lettuce library.
I took packet capture / wireshark on my application.
I saw one packet (from application ...
- 2,983
1
vote
1
answer
106
views
Ping/Pong message system in Java between clients and a server over TCP sockets
I need to create a connection between 4 clients and a server and they should communicate over a networkprotocol.
I'm quite clueless and I don't know what I need to implement in which class. I managed ...
- 11