Qt joinmulticastgroup. Please see the comment in Multicast.

Qt joinmulticastgroup. This function was introduced in Qt 4. d/iptables stop and then try the example multicastsender and multicastreceiver examples that came with Qt. Jan 27, 2021 · To start viewing messages, select the forum that you want to visit from the selection below. If I send the message in the same computer I don't have this problem. 250/1900 is UPnP multicast. 1 <none> lo0 Use joinMulticastGroup () and leaveMulticastGroup () to control group membership, and QAbstractSocket::MulticastTtlOption and QAbstractSocket::MulticastLoopbackOption to set the TTL and loopback socket options. 9 on KDAB Codebrowser Multicast UDP on raspberry pi I haven't narrowed things down enough to know if my issue is because of debian, raspbian specifically, or if I am just missing a something completely. Jul 27, 2025 · 本文探讨了在Windows系统中使用两个物理网卡，并且每个网卡设置IPv4和IPv6地址的情况下，如何正确地实现组播数据的发送。 作者在尝试使用QT的QUdpSocket加入组播组时遇到了问题，当启用IPv6时，只有一张网卡能够成功加入组播组。 In this example we'll learn how to use the QUdpSocket class to send and receive multicast messages on the network. Recently I am developing May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? Qt 是一个跨平台C++图形界面开发库，利用Qt可以快速开发跨平台窗体应用程序，在Qt中我们可以通过拖拽的方式将不同组件放到指定的位置，实现图形化开发极大的方便了开发效率，本章将重点介绍如何运用`QUdpSocket`组件实现基于UDP的组播通信。组播是一种一对多的通信方式，允许一个发送者将数据报文 Jan 14, 2018 · sockets - UDP multicast from specific network card - Stack Overflow c++ - Qt: joinMulticastGroup for all interface - Stack Overflow sockets - Qt QUdpSocket fails to receive multicast udp packets on a specific interface - Stack Overflow [QTBUG-27641] Multicast joining fails on multiple interfaces - Qt Bug Tracker Multicast/Broadcast questions Description The Multicast Sender example shows how to send information to multiple clients in a multicast group. I'm able to send messages from Windows to Mac, but not from Mac to Windows. QUdpSocket also could not be joined to the multicast group QHostAddress (224. Sep 30, 2016 · bool QUdpSocket::joinMulticastGroup(const QHostAddress &groupAddress, const QNetworkInterface &iface) You can define the interface that has to be used for sending the mutlicast massages. After looking into the source code of qnativesocketengine_*. 6. Oct 6, 2013 · 如何在Qt中正确使用joinMulticastGroup接口？ 在Windows中，我有两个物理接口。 在每个接口上设置两个IP地址: IPv4和IPv6。 以下代码在此配置中不正确： joinMulticastGroup 只为第一个接口返回 true，对于下一个接口， joinMulticastGroup 返回 false。 The following code doesn't correct working in this configuration: joinMulticastGroup return true only for first interface and for next interface joinMulticastGroup return false. When trying to use QUdpSocket::joinMulticastGroup with multiple interfaces it often fails under certain conditions. 25. How can I force it to send data by that interface? It is tested with SmartSniff. Goal of this library is to provide a cleaner interface for sending and receiving UDP Multicast data. Jul 11, 2017 · I tried to use QUdpSocket->joinMulticastGroup (), supplying a specific QNetworkInterface for message receipt. Leaves the multicast group specified by groupAddress on the interface iface. But still, I can't see the messages in the specific VLAN the udpsocket is bind to. io Aug 7, 2025 · 文章浏览阅读5k次，点赞3次，收藏3次。本文探讨了在QT中使用QUdpSocket时遇到的问题：加入组播组失败。作者总结了两种常见错误原因：（1）绑定协议非IPv4；（2）加入组播前未绑定端口。通过正确绑定IPv4协议及端口，可以有效解决此类问题。 Note: This function should be called with the same arguments as were passed to joinMulticastGroup (). May 12, 2021 · 0 nagesh 12 May 2021, 16:23 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv-> joinMulticastGroup ( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? May 4, 2021 · This problem causes app to not being able to join multicast groups on UWP platform. Aug 7, 2024 · Qt的QUdpSocket组件支持基于UDP的组播通信，实现一对多数据传输。通过setSocketOption设置TTL，bind绑定端口，joinMulticastGroup加入组播，writeDatagram发送数据，readDatagram接收数据，leaveMulticastGroup退出组播。 Nov 25, 2021 · Hi, These lines of code QUSServer= new QUdpSocket(this); QUSServer->bind(3702, QAbstractSocket::DontShareAddress | QAbstractSocket::ReuseAddressHint) Oct 20, 2011 · Qt 4. I am interested in the leaveMulticastGroup. 0k Views 1 Watching Oldest to Newest joinMulticastGroup(groupAddress, iface) Parameters: groupAddress – QHostAddress iface – QNetworkInterface Return type: bool Joins the multicast group address groupAddress on the interface iface. 0. But I don't understand the leaveMulticastGroup in the multicast when I read the Qt document. 0 MinGW 64 bit, Win10 Pro 0 ThirdStrand 23 Sep 2021, 09:09 Interesting: In Linux Qt 5. May 22, 2016 · I was recently dealing with multicast and Qt, and this problem seems to still exist with Qt 5. May 27, 2020 · This code runs fine on Windows 10 x64 (Qt 5. Please see the comment in Multicast. Oct 22, 2013 · 1 My Qt application uses multicast QUdpSocket and need half-duplex operation (it simulates radio transfer between simplex radiostations). Demonstrates how to receive information sent to a multicast group. If you are looking for information about Qt related issue — register and post your question. 10 port 3665), in Windows all done! it's fine. 250. 3. But, if I disable IPv6 on both interfaces joinMulticastGroup join all interfaces. QUdpSocket also supports UDP multicast. It's acting like a simple chat program within a local network. 2, Qt 5. May 31, 2021 · Hello. I tried it a moment ago on my laptop and it worked. 255. But also it must support working multiple instances on same machine (user explicitly selects loopback interface). This section describes the Windows implementation Use joinMulticastGroup () and leaveMulticastGroup () to control group membership, and QAbstractSocket::MulticastTtlOption and QAbstractSocket::MulticastLoopbackOption to set the TTL and loopback socket options. On Linux, the bytesReceived slot is called the first time a datagram arrives, and the socket->hasPendingDatagrams () call returns true, but the QNetworkDatagram object returned by the socket->receiveDatagram () call is not valid. bind(QHostAddress::Any, 2222); then eventual May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? Oct 12, 2013 · Hi, I have a big problem, I developed an application that join a Multicast group (225. It didn't work (my app wasn't receiving messages that wireshark was showing). 1. 255) but your code doesn't contain any joinMulticastGroup call Oct 20, 2011 · Qt 4. 2 when another process is already bound on the specified port. This code is tested with a gcc compiler in linux and can be modified to work with windows or any other operating system with miniamal changes. qt. 8. In the next step we connect the readyRead () signal of the socket, which is emitted whenever a new datagram arrived, against our own slot processPendingDatagrams (). Qt Centre is a community site devoted to programming in C++ using the Qt framework. Using the method "joinMulticastGroup" for each individual address takes very long: For example: On Mac OS X it took several seconds, on May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? QUdpSocket also supports UDP multicast. 255 Aug 29, 2022 · Give me this result on the 1st PC: Interface: "Ethernet" Interface: "VirtualBox Host-Only Network" Interface: "Ethernet 2" Interface: "Wi-Fi" Interface: "Local Area Connection* 1" Interface: "Local Area Connection* 2" Interface: "Bluetooth Network Connection" Interface: "Loopback Pseudo-Interface 1" When I run the sender / receiver on that PC, I am only seeing the multicast messages with Nov 5, 2014 · Hello, I am writing an UDP client where I have to listen to the multicast address range 239. Oct 12, 2013 · Hi, I have a big problem, I developed an application that join a Multicast group (225. cpp I found the following code that is actually incorrect: Jun 12, 2015 · For some reason I just recently ran into an issue with this. But you don't get any incoming data through the readyRead() signal? That's rather strange. Then I provided the APIs to join and leave multicast groups. May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? But I don't understand the leaveMulticastGroup in the multicast when I read the Qt document. See also multicastInterface (), joinMulticastGroup (), and leaveMulticastGroup (). After calling the JoinMulticastGroup method, the underlying Socket sends an Internet Group Management Protocol (IGMP) packet to the router requesting membership to the multicast group. html#joinMulticastGroup ? Jul 29, 2014 · So, I want to use QUdpSocket::joinMulticastGroup () and not be concerned with OS specific calls, but have not found a way to only join the multicast group that originates from a specified source. Oct 9, 2013 · I want join both interfaces to multicast group, but joinMulticastGroup can't join both interfaces, and join only first interface. cpp qtbase v5. That's weird. 0 (same version) gcc, binding to the Multicast IPv4 QHostAddress works, then join to the multicast group with the same address. Currently, I am running Fedora 15 with SE Aug 17, 2006 · Hi everyone, I have a simple question : has someone actually managed to write a multicast packet receiver app using ONLY the Qt library 4. Regards! The second time the following error message is printed to console: QNativeSocketEngine::joinMulticastGroup () was not called in QAbstractSocket::BoundState 239. 2. The same code runs just fine on Windows (non-UWP), Ubuntu, Android, iOS May 12, 2021 · @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinm When trying to use QUdpSocket::joinMulticastGroup with multiple interfaces it often fails under certain conditions. 1 and above, in other words using pure Qt code ? If this is the case I would be very interested to know how it works :) Best regards, Julien. 12. exe) it looks like it registers to multica May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? Feb 10, 2011 · Until Qt provides native, cross-platform multicast support, you will have to manage some platform specific code. Feb 28, 2020 · udpSocket->joinMulticastGroup(groupAddress,_interface)); But, I use netstat command , I find the en0 join the multicast group, not my designated en6 IPv4 Multicast Group Memberships Group Link-layer Address Netif 224. bool QUdpSocket:: leaveMulticastGroup (const QHostAddress & groupAddress, const QNetworkInterface & iface) This is an overloaded function. The ShareAddress flag should allow binding multiple times however. 1 to 239. Both of them join a pre Jan 5, 2015 · I want to send data via a specific network interface udpSocket->joinMulticastGroup(QHostAddress(Address), QNetworkInterface::interfaceFromName(iface)); but, data is sending via another network interface. porting application We also have to tell the socket which multicast group we want to join, that's done by calling joinMulticastGroup (). Over 90 percent of questions asked here gets answered. I recently search the multicast because I have to use the multicast in my developing app. Mar 1, 2018 · I have a multicast camera on ip 225. Aug 25, 2021 · @SGaist I change value of group address but same In another device (Jetson nano), i can join successfully but cannot receive data . 8->Network->QUdpSocket->Multicast->joinMulticastGroup () problem General and Desktop 3 Posts 3 Posters 10. The example application is splitted in two executables, multicastsender and multicastreceiver. This is the constructor of my class: Discovery::Discovery(QObject *parent):QObject(parent) { groupAddress = This example demonstrates how to receive messages sent to a multicast group Example project @ code. I have a python Qt: joinMulticastGroup for all interface，代码先锋网，一个为软件开发程序员提供代码片段和技术文章聚合的网站。 Aug 8, 2017 · I have been using Qt for desktop applications programming for a quite long time, but I am totally a newbie in network programmings. The application listens for data on a multicast address on a team0 interface (I also have a eno1 interface for output of The second time the following error message is printed to console: QNativeSocketEngine::joinMulticastGroup () was not called in QAbstractSocket::BoundState 239. 8->Network->QUdpSocket->Multicast->joinMulticastGroup () problem Jul 9, 2024 · 文章浏览阅读1w次，点赞14次，收藏85次。该博客围绕UDP组播展开，介绍了UDP组播特性和组播IP地址，重点阐述了使用Qt实现UDP组播程序的步骤，包括声明变量、槽函数，初始化socket、加入和退出组播、发送和读取消息等，还展示了程序演示效果，多个程序加入同组可互收消息。 Oct 20, 2011 · Hi, I have had this problem before. Use joinMulticastGroup() and leaveMulticastGroup() to control group membership, and MulticastTtlOption and MulticastLoopbackOption to set the TTL and loopback socket options. io/qt-5/qudpsocket. I am running Centos 7. Multicast programming is enabled through Windows Sockets. Perhaps you could try wireshark or another packet sniffer to see if packages are Dec 20, 2024 · （3）加入到组播IP，函数为 joinMulticastGroup（4）可随时退出该组播IP，函数为leaveMulticastGroup2、发送方与点对点的UDP编程步骤完全相同，不同之处只有一点：目标. May 31, 2021 · @morita Did you also read https://doc. Welcome to Qt Centre. Multicast is a kind of UDP traffic similar to BROADCAST, but only hosts that have explicitly Apr 15, 2017 · QT下的类 QUdpSocket 仅提供了加入组播的功能 joinMulticastGroup，却没有提供加入SSM的功能。 分析了一下QUdpSocket的源码，发现joinMulticastGroup仅是socket函数 setsocketoption的一个简单封装，隐藏了不同系统下实现的不同。于是参考了QT的源码，自己写了一个加入SSM的功能，代码见下面。目前只支持window下运行 Jan 7, 2021 · Multicast programming is enabled through Windows Sockets. Use setMulticastInterface () to control the outgoing interface for multicast datagrams, and multicastInterface () to query it. The problem is that joinMulticastGroup() uses the first address of the interface without checking if it's IPV4 or IPV6 (even if you use AnyIpv4 in bind). See also joinMulticastGroup (). porting application Mar 4, 2021 · In order receive multicast data joinMulticastGroup API call to be called with the multicast group address. 251 <none> lo0 224. May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? May 3, 2021 · I printed the flags for network interfaces and they show that no interface has CanMulticast flag set. And I couldn't find any samples for the leaveMulticastGroup. It turned out to be the firewall on my fedora system. Use setMulticastInterface() to control the outgoing interface for multicast datagrams, and multicastInterface() to query it. Could you tell me how to use it and which situation to use it ? Aug 18, 2016 · I an writing a Programm in Qt which should discover Routers in a LAN via UPnP. qint64 QUdpSocket:: writeDatagram (const char * data, qint64 size, const QHostAddress & address, quint16 port) Sends the datagram at data of size size to the host address address at port port. porting application To reproduce: computer with multiple NICs, connected to multiple networks modify multicastreceiver example by specifying an interface in: udpSocket->joinMulticastGroup(groupAddress, <interface>); run multicastsender on some other machine on those networks For some reason it still listens the default interface Oct 12, 2013 · Please I need help my brain is near to explosion!! Use joinMulticastGroup () and leaveMulticastGroup () to control group membership, and QAbstractSocket::MulticastTtlOption and QAbstractSocket::MulticastLoopbackOption to set the TTL and loopback socket options. I printed the flags for network interfaces and they show that no interface has CanMulticast flag set though those network interfaces can multicast. 0 to 239. 15. 8->Network->QUdpSocket->Multicast->joinMulticastGroup () problem General and Desktop Posts Posters Views Oldest to Newest May 24, 2025 · 一、概述 Qt 组播实现起来比较简单，基本步骤是先绑定IP地址和端口，然后加入组播组，将网卡数据准备完成信号与一个数据接收处理的槽函数连接即可。但是如果计算机上多于两块网卡，就必须再增加两个步骤才行：使用 setMulticastInterface 设置组播网卡，然后加入组播的同时指定网卡 joinMulticastGroup Oct 10, 2019 · sqtSocket = new QUdpSocket (this); groupAddress = QStringLiteral ("225. cpp. With QUdpSocket , you can also establish a virtual May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? Multicast Sender Demonstrates how to send messages to a multicast group. 8 MSVC 2017), but does not on Ubuntu 18. To reproduce: computer with multiple NICs, connected to multiple networks modify multicastreceiver example by specifying an interface in: udpSocket->joinMulticastGroup(groupAddress, <interface>); run multicastsender on some other machine on those networks For some reason it still listens the default interface Nov 28, 2016 · @marinas said in QUdpSocket seems to stop receiving data from multicast group: I have tried debugging it and the only thing happening is that the sendDatagram () method is still called every 100 ms as the timer times out. 8->Network->QUdpSocket->Multicast->joinMulticastGroup () problem General and Desktop Posts Posters Views Oldest to Newest Oct 7, 2013 · 问题是 joinMulticastGroup() 使用接口的第一个地址而不检查它是 IPV4 还是 IPV6（即使您在绑定中使用 AnyIpv4）。 这个问题在官方 Qt 版本中没有得到修复，但建议的补丁对我有用： This function was introduced in Qt 4. For example, if you are targeting Windows, I extended the QUdpSocket class into my own MulticastSocket class. So I have no choice but to use plain C/C++. 7. But when i start playing with ffplayer (ffplay. Qt官方提供了如下几个在您的应用中使用 QUdpSocket 的示例： Broadcast Sender，Broadcast Receiver， Multicast Sender 和 Multicast Receiver。 您也可以在 QTcpSocket 和 QNetworkDatagram 文档中找到相关信息。 Oct 26, 2013 · Please, help setup sockets to receive and send multicast datagrams in following scenario: user selects network interface (because it may have multiple networ Oct 20, 2011 · Qt 4. cpp I found the following code that is actually incorrect: Sep 30, 2016 · bool QUdpSocket::joinMulticastGroup(const QHostAddress &groupAddress, const QNetworkInterface &iface) You can define the interface that has to be used for sending the mutlicast massages. Use joinMulticastGroup () and leaveMulticastGroup () to control group membership, and QAbstractSocket::MulticastTtlOption and QAbstractSocket::MulticastLoopbackOption to set the TTL and loopback socket options. Windows Sockets enables the Multicast Listener Discovery (MLD) versions 1 (MLDv1) and 2 (MLDv2) on IPv6 and the Internet Group Management Protocol versions 2 (IGMPv2) and 3 (IGMPv3) through the use of socket options or IOCTLs. Sep 8, 2014 · The simple code belows fails on Windows with QT5. d/init. So I believe that is the reason, why socket fails to join multicast group if no checks made. MC datagrams flow like butter! There are evidently significant differences in how UDP and Multicast work between the two Use joinMulticastGroup () and leaveMulticastGroup () to control group membership, and QAbstractSocket::MulticastTtlOption and QAbstractSocket::MulticastLoopbackOption to set the TTL and loopback socket options. 8 GCC). On MacOSX it works Source code of qtbase/src/network/socket/qudpsocket. So I believe that is the reason, why socket fails to jo Nov 7, 2024 · 最近在某个项目中，发现了一个低版本Qt的bug，导致组播无法正常使用，经过一番排查，终于找到了原因，特此记录。 环境 Qt：5. 6 and Win7. We would like to show you a description here but the site won’t allow us. On my computer, I can play video in VLC over LAN card or Wi-Fi. May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? We would like to show you a description here but the site won’t allow us. 0 mingw32 操作系统：windows 11 现象 Qt Multicast Error QNativeSocketEngine::joinMulticastGroup () was not called in QAbstractSocket::BoundState, Programmer Sought, the best programmer technical posts May 12, 2021 · nagesh wrote on 12 May 2021, 16:23 #5 @w-tkm said in QUdpSocket Multicast can't receive: m_pUdpSockRecv->joinMulticastGroup( QHostAddress( m_strConnectHostIp ) ) @w-tkm The address used in Joinmulticastgroup is multicast series ip address right? A simple c++ library to send and receive udp multicast. _joinmulticastgroup Oct 12, 2013 · Please I need help my brain is near to explosion!! Aug 24, 2017 · Hi, I'm having trouble getting data into my Qt5 application. It means that one application instance must not receive datagrams it sends. (multicast series from 224. If your system is not publicly available try the following command on the shell as root /etc/rc. The JoinMulticastGroup method subscribes the UdpClient to a multicast group using the specified IPAddress. I'm not sure if it is a Qt problem or a linux configuration problem, i believe I have almost exhausted my Linux troubleshooting so am looking at the Qt code as the possible problem. The multicast address range is 224. I configure the bind the following way: m_udpSocket. 3"); sqtSocket->bind (QHostAddress::AnyIPv4,, 3003, QUdpSocket::ShareAddress) sqtSocket->joinMulticastGroup (groupAddress) ; I send the message between 2 computer with ethernet. Dec 27, 2024 · Multicast Receiver ExampleL'article Publié le 27 décembre 2024 - Mis à jour le 27 décembre 2024 Note: This function should be called with the same arguments as were passed to joinMulticastGroup (). 1) with default IPv4 interface, corresponding joinMulticastGroup always returns false! Note: This function should be called with the same arguments as were passed to joinMulticastGroup (). Home Qt Development General and Desktop Qt 4. 1 - 239. 04 x64 (Qt 5. May 12, 2021 · Qt 5. Jan 14, 2016 · I use an experimental project to test Qt multicast. 2oftg y3 nvx4k prx qccho ztq i0zxc t926 1c ho5mt