networking

问题 I have spent some time learning Java and in doing so have built myself a rather complex game. My game is a desktop ran swing app which after play results in a score value that gets entered onto a leaderboard. The game is pretty much complete, except a few security mechanisms. At first I never intended to have my game connected to the net as the phrase 'networking' has always put me off. Now that my game has slowly developed, it has actually turned out far better than I had imagined which has

问题 Can I perform a UDP broadcast packets on my machine? I don't have a network, i just have my cheap linux box. I want to have a server broadcasting a packet and two or more clients in the same machine receiving them. Is that possible? What IP do I use? @gravyface gave me hope but I tried: 1) server sending to 127.255.255.255:54321 and clients listenting to 0.0.0.0:54321. 2) server sending to 127.255.255.255:54321 and clients listening to 127.0.0.1:54321. 3) server sending to 127.255.255.255

问题 Can I perform a UDP broadcast packets on my machine? I don't have a network, i just have my cheap linux box. I want to have a server broadcasting a packet and two or more clients in the same machine receiving them. Is that possible? What IP do I use? @gravyface gave me hope but I tried: 1) server sending to 127.255.255.255:54321 and clients listenting to 0.0.0.0:54321. 2) server sending to 127.255.255.255:54321 and clients listening to 127.0.0.1:54321. 3) server sending to 127.255.255.255

问题 If i open a raw socket, and send udp packets with a wrong checksum, would the packets be dropped other side by the tcp/ip stack? 回答1: Yes they would be dropped. If you need more reliable communication you're much better off using TCP. for more information, take a look at this: http://www.diffen.com/difference/TCP_vs_UDP UDP there's no guarantee that the packets will even be sent, let alone received. If they are in fact received though, they are checked. If they fail checksum they are dropped.

问题 Friends, I think it is a strange thing (at least for me). Coz I have learnt that every domain name on the Internet has itself a corresponding IP address. And it is stored at some place on a DNS. Now, This is what I get when I ping google.com from my command line. C:\Windows\system32>ping google.com Pinging google.com [74.125.236.135] with 32 bytes of data: Reply from 74.125.236.135: bytes=32 time=10ms TTL=55 Reply from 74.125.236.135: bytes=32 time=11ms TTL=55 Reply from 74.125.236.135: bytes

问题 Linux has ioctl SIOCOUTQ described in man-page tcp(7) that returns amount of unsent data in socket buffers. If I understand kernel code right, all the non-ACKed data is counted as "unsent". The ioctl is available at least since 2.4.x. Is there anything alike for {Free,Net,Open,*}BSD, Solaris, Windows? 回答1: There are (at least) two different pieces of information you might want: the amount of data that hasn't been sent yet, and the amount of data that's been sent-but-not-ACK-ed. On Linux:

问题 Linux has ioctl SIOCOUTQ described in man-page tcp(7) that returns amount of unsent data in socket buffers. If I understand kernel code right, all the non-ACKed data is counted as "unsent". The ioctl is available at least since 2.4.x. Is there anything alike for {Free,Net,Open,*}BSD, Solaris, Windows? 回答1: There are (at least) two different pieces of information you might want: the amount of data that hasn't been sent yet, and the amount of data that's been sent-but-not-ACK-ed. On Linux:

问题 I am building a React Native mobile application that is using a Laravel backend, currently running on localhost:8000. When making a fetch request from an Android device to my server, my application gets the following error logs: My code is below: export default class App extends Component { login() { fetch('http://localhost:8000/api/establishments/get') .then((response) => response.json()) .then((responseJson) => { console.log('success!'); }) .catch((error) => { console.error(error); }); }

问题 I am building a React Native mobile application that is using a Laravel backend, currently running on localhost:8000. When making a fetch request from an Android device to my server, my application gets the following error logs: My code is below: export default class App extends Component { login() { fetch('http://localhost:8000/api/establishments/get') .then((response) => response.json()) .then((responseJson) => { console.log('success!'); }) .catch((error) => { console.error(error); }); }

问题 I am facing issue with accessing Open stack VM's on LAN. I have setup single machine(192.168.2.15) opensatck using devstack, so all VM's are running inside this machine My machine(192.168.2.15) has one network card(eth0) and I have nova networking, have not installed neutron. I have assigned static IP on eth0 of all the LAN machine( such as 192.168.2.15 and 192.168.2.16) in /etc/network/interfaces file. System information of the Openstack Machine is as below: Memory usage: 19% IP address for