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  • Getting into the details of game engine programming

    - by Darkslash
    I am interested in learning game programming, but I really have an interest in the lower level engineering in games. I have OpenGL experience, and I am really interested in learning more about implementing AI, Physics, etc. I have a computer science degree, so I really like getting into technical stuff. Many times when I ask about this sort of thing, I get a lot of "Use an engine", "Use Unity3d", "Why waste your time writing code that already exists", etc, etc. My idea was to use simpler libraries such as SFML or XNA so that I could learn how to implement the more complex systems. The thing is, although I do want to write games, I want to learn things that using something like Unity simply doesn't teach you. My goal is not to make a current generation quality 3D game to sell, I just want to make some cool smaller games and learn all I can about the programming side of game development. Is this something that people just do not do anymore? It seems like everywhere I turn people are using Unity or UDK or GameMaker. I fully understand why you would use a tool like these, but I cant see how they would suit my purposes. So where does someone like myself turn? Am I trying to learn something that people just do not bother doing anymore? Is the innovation in this area gone and just all about gameplay now? I'm sorry if this question seems silly, but I am genuinely interested in knowing more about this and meeting more people who are interested in this sort of thing.

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  • webgame engine how does it works

    - by TWCrap
    Hy all, first off all, don't yell that i shouldn't start with it, i just want to know how that works... The thing is, how does the engine of an webgame works. A game like tribalwars, grepolis and forge of empires. How does that keeping alive work. I mean, a user is building an building, and quit the browser... The building is build even when the session of the user is expired. but the points of the user is updated when the building is finished... So how does that works. What do you guys think? do they have some kind of cronjob that is fired every second, and that walks throug the database, and search for finished buildings, and update's the stuff? or do you guys think that they do it difrent?!? I hope that i was clear. -NOTE- i don't need anny code, i'm just intrested in the progress behind the game... Greetingz Marc

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  • Can't seem to get C TCP Server-Client Communications Right

    - by Zeesponge
    Ok i need some serious help here. I have to make a TCP Server Client. When the Client connects to server using a three stage handshake. AFterwards... while the Client is running in the terminal, the user enters linux shell commands like xinput list, ls -1, ect... something that uses standard output. The server accepts the commands and uses system() (in a fork() in an infinite loop) to run the commands and the standard output is redirected to the client, where the client prints out each line. Afterward the server sends a completion signal of "\377\n". In which the client goes back to the command prompt asking for a new command and closes its connection and exit()'s when inputting "quit". I know that you have to dup2() both the STDOUT_FILENO and STDERR_FILENO to the clients file descriptor {dup2(client_FD, STDOUT_FILENO). Everything works accept when it comes for the client to retrieve system()'s stdout and printing it out... all i get is a blank line with a blinking cursor (client waiting on stdin). I tried all kinds of different routes with no avail... If anyone can help out i would greatly appreciate it TCP SERVER CODE include #include <sys/socket.h> #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <signal.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> //Prototype void handle_client(int connect_fd); int main() { int server_sockfd, client_sockfd; socklen_t server_len, client_len; struct sockaddr_in server_address; struct sockaddr_in client_address; server_sockfd = socket(AF_INET, SOCK_STREAM, 0); server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = htonl(INADDR_ANY); server_address.sin_port = htons(9734); server_len = sizeof(server_address); bind(server_sockfd, (struct sockaddr *)&server_address, server_len); /* Create a connection queue, ignore child exit details and wait for clients. */ listen(server_sockfd, 10); signal(SIGCHLD, SIG_IGN); while(1) { printf("server waiting\n"); client_len = sizeof(client_address); client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_address, &client_len); if(fork() == 0) handle_client(client_sockfd); else close(client_sockfd); } } void handle_client(int connect_fd) { const char* remsh = "<remsh>\n"; const char* ready = "<ready>\n"; const char* ok = "<ok>\n"; const char* command = "<command>\n"; const char* complete = "<\377\n"; const char* shared_secret = "<shapoopi>\n"; static char server_msg[201]; static char client_msg[201]; static char commands[201]; int sys_return; //memset client_msg, server_msg, commands memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(client_msg)); memset(&commands, 0, sizeof(commands)); //read remsh from client read(connect_fd, &client_msg, 200); //check remsh validity from client if(strcmp(client_msg, remsh) != 0) { errno++; perror("Error Establishing Handshake"); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write remsh to client write(connect_fd, remsh, strlen(remsh)); //read shared_secret from client read(connect_fd, &client_msg, 200); //check shared_secret validity from client if(strcmp(client_msg, shared_secret) != 0) { errno++; perror("Invalid Security Passphrase"); write(connect_fd, "no", 2); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write ok to client write(connect_fd, ok, strlen(ok)); // dup2 STDOUT_FILENO <= client fd, STDERR_FILENO <= client fd dup2(connect_fd, STDOUT_FILENO); dup2(connect_fd, STDERR_FILENO); //begin while... while read (client_msg) from server and >0 while(read(connect_fd, &client_msg, 200) > 0) { //check command validity from client if(strcmp(client_msg, command) != 0) { errno++; perror("Error, unable to retrieve data"); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write ready to client write(connect_fd, ready, strlen(ready)); //read commands from client read(connect_fd, &commands, 200); //run commands using system( ) sys_return = system(commands); //check success of system( ) if(sys_return < 0) { perror("Invalid Commands"); errno++; } //memset commands memset(commands, 0, sizeof(commands)); //write complete to client write(connect_fd, complete, sizeof(complete)); } } TCP CLIENT CODE #include <sys/types.h> #include <sys/socket.h> #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> #include "readline.c" int main(int argc, char *argv[]) { int sockfd; int len; struct sockaddr_in address; int result; const char* remsh = "<remsh>\n"; const char* ready = "<ready>\n"; const char* ok = "<ok>\n"; const char* command = "<command>\n"; const char* complete = "<\377\n"; const char* shared_secret = "<shapoopi>\n"; static char server_msg[201]; static char client_msg[201]; memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(server_msg)); /* Create a socket for the client. */ sockfd = socket(AF_INET, SOCK_STREAM, 0); /* Name the socket, as agreed with the server. */ memset(&address, 0, sizeof(address)); address.sin_family = AF_INET; address.sin_addr.s_addr = inet_addr(argv[1]); address.sin_port = htons(9734); len = sizeof(address); /* Now connect our socket to the server's socket. */ result = connect(sockfd, (struct sockaddr *)&address, len); if(result == -1) { perror("ACCESS DENIED"); exit(1); } //write remsh to server write(sockfd, remsh, strlen(remsh)); //read remsh from server read(sockfd, &server_msg, 200); //check remsh validity from server if(strcmp(server_msg, remsh) != 0) { errno++; perror("Error Establishing Initial Handshake"); close(sockfd); exit(1); } //memset server_msg memset(&server_msg, 0, sizeof(server_msg)); //write shared secret text to server write(sockfd, shared_secret, strlen(shared_secret)); //read ok from server read(sockfd, &server_msg, 200); //check ok velidity from server if(strcmp(server_msg, ok) != 0 ) { errno++; perror("Incorrect security phrase"); close(sockfd); exit(1); } //? dup2 STDIN_FILENO = server socket fd? //dup2(sockfd, STDIN_FILENO); //begin while(1)/////////////////////////////////////// while(1){ //memset both msg arrays memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(server_msg)); //print Enter Command, scan input, fflush to stdout printf("<<Enter Command>> "); scanf("%s", client_msg); fflush(stdout); //check quit input, if true close and exit successfully if(strcmp(client_msg, "quit") == 0) { printf("Exiting\n"); close(sockfd); exit(EXIT_SUCCESS); } //write command to server write(sockfd, command, strlen(command)); //read ready from server read(sockfd, &server_msg, 200); //check ready validity from server if(strcmp(server_msg, ready) != 0) { errno++; perror("Failed Server Communications"); close(sockfd); exit(1); } //memset server_msg memset(&server_msg, 0, sizeof(server_msg)); //begin looping and retrieving from stdin, //break loop at EOF or complete while((read(sockfd, server_msg, 200) != 0) && (strcmp(server_msg, complete) != 0)) { //while((fgets(server_msg, 4096, stdin) != EOF) || (strcmp(server_msg, complete) == 0)) { printf("%s", server_msg); memset(&server_msg, 0, sizeof(server_msg)); } } }

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  • Search Engine Optimization - The Importance of Page Optimization in Search Engine Optimization

    In order for your website to rank well, your internal linking structure is critical to your success. This is covered some of the theory for this in various articles and blogs about Page Structure of a website, which said how you should map out the physical linking structure, but in this guide I will explain more about the importance of interlinking your pages, while using your targeted keyword in your anchor text.

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  • Which Game Engine to Use for an Angry Bird style game? [JAVA] [on hold]

    - by Arch1tect
    Our team is building an Angry Bird Style game, and we have only about ten days. The game is a little more complex than Angry Bird because there are two players, they each have a castle with pigs to protect(not destroy:)). And the goal is to destroy the other player's pigs. I wonder what Game Engine would help us finish this game most efficiently. We at least need a physics engine but I guess game engine is more helpful since it usually includes physics engine. Correct me if I'm wrong. (So I'm wondering which game engine I should use, if it's just physics engine, I'll use box2d) Networking may or may not be added later depend on time we have. Thanks in advance for any advice! EDIT: image looks small, I'll add one:

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  • Is there a pedagogical game engine?

    - by K.G.
    I'm looking for a book, website, or other resource that gives modern 3D game engines the same treatment as Operating Systems: Design and Implementation gave operating systems. I have read Jason Gregory's Game Engine Architecture, which I enjoyed. However, by intent the author treated components of the architecture as atomic units, whereas what I'm interested in is the plumbing between those units that makes a coherent whole out of ideally loosely coupled parts. In books such as these, one usually reads that "that's academic," but that's the point! I have also read Julian Gold's Object-oriented Game Development, which likewise was good, but I feel is beginning to show its age. Since even mobile platforms these days are multicore and have fast video memory, those kinds of things (concurrency, display item buffering) would ideally be covered. There are other resources, such as the Doom 3 source code, which is highly instructive for its being a shipped product. The problem with those is as follows: float Q_rsqrt( float number ) { long i; float x2, y; const float threehalfs = 1.5F; x2 = number * 0.5F; y = number; i = * ( long * ) &y; // evil floating point bit level hacking i = 0x5f3759df - ( i >> 1 ); // what the f***? y = * ( float * ) &i; y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration // y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed return y; } To wit, while brilliant, this kind of source requires more enlightenment than I can usually muster upon first read. In summary, here's my white whale: For an adult reader with experience in programming. I wish I could save all the trees killed by every. Single. Game Programming book ever devoting the first two chapters to "Now just what is a variable anyway?" In C or C++, very preferably C++. Languages that are more concise are fantastic for teaching, except for when what you want to learn is how to cope with a verbose language. There is also the benefit of the guardrails that C++ doesn't provide, such as garbage collection. Platform agnostic. I'm sincerely afraid that this book is out there and it's Visual C++/DirectX oriented. I'm a Linux guy, and I'd do what it takes, but I would very much like to be able to use OpenGL. Thanks for everything! Before anyone gets on my case about it, Fast inverse square root was from Quake III Arena, not Doom 3!

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  • Zooming in isometric engine using XNA

    - by Yheeky
    I´m currently working on an isometric game engine and right now I´m looking for help concerning my zoom function. On my tilemap there are several objects, some of them are selectable. When a house (texture size 128 x 256) is placed on the map I create an array containing all pixels (= 32768 pixels). Therefore each pixel has an alpha value I check if the value is bigger than 200 so it seems to be a pixel which belongs to the building. So if the mouse cursor is on this pixel the building will be selected - PixelCollision. Now I´ve already implemented my zooming function which works quite well. I use a scale variable which will change my calculation on drawing all map items. What I´m looking for right now is a precise way to find out if a zoomed out/in house is selected. My formula works for values like 0,5 (zoomed out) or 2 (zoomed in) but not for in between. Here is the code I use for the pixel index: var pixelIndex = (int)(((yPos / (Scale * Scale)) * width) + (xPos / Scale) + 1); Example: Let´s assume my mouse is over pixel coordinate 38/222 on the original house texture. Using the code above we get the following pixel index. var pixelIndex = ((222 / (1 * 1)) * 128) + (38 / 1) + 1; = (222 * 128) + 39 = 28416 + 39 = 28455 If we now zoom out to scale 0,5, the texture size will change to 64 x 128 and the amount of pixels will decrease from 32768 to 8192. Of course also our mouse point changes by the scale to 19/111. The formula makes it easy to calculate the original pixelIndex using our new coordinates: var pixelIndex = ((111 / (0.5 * 0.5)) * 64) + (19 / 0.5) + 1; = (444 * 64) + 39 = 28416 + 39 = 28455 But now comes the problem. If I zoom out just to scale 0.75 it does not work any more. The pixel amount changes from 32768 to 18432 pixels since texture size is 96 x 192. Mouse point is transformed to point 28/166. The formula gives me a wrong pixelIndex. var pixelIndex = ((166 / (0.75 * 0.75)) * 96) + (28 / 0.75) + 1; = (295.11 * 96) + 38.33 = 28330.66 + 38.33 = 28369 Does anyone have a clue what´s wrong in my code? Must be the first part (28330.66) which causes the calculation problem. Thanks! Yheeky

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  • Google Search Engine Optimization - The 3 Step Process to Search Engine Domination

    Would you like more targeted traffic to your website? Would you like to know how to get a stream of profitable customers visiting your site for keywords people are actually searching for? Are you overwhelmed by the complexity of SEO? If you answered yes to any of these questions then the easy 3 step Strategy to Google domination is exactly what you are looking for. In this article I reveal the 3 simple tactics for consistent top ten rankings.

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  • TCP RST right after FIN/ACK

    - by Nitzan Shaked
    I am having the weirdest issue: I have a web server which sometimes, only on very specific requests, will send a RST to the client after having sent the FIN datagram. First, a description of the setup: The server runs on an Ubuntu 12.04.1 LTS, which itself is a VM guest inside a Win7 x64 host, in bridged mode. ufw is disabled on the host The client runs on a iOS simulator, which runs on OS X Mountain Lion, which is a VM guest (hackintosh) inside a Win7 x64 host, in bridged mode. Both client and server are on the same LAN, one is connected to the home router via an Ethernet cable, and then other thru WiFi. I happened to glimpse over the server's http logs and found that the client sometimes issuing multiple subsequent identical requests. Further investigation led me to discover that this happens when the server sends a RST, and that the client is simply re-trying. I am attaching several tcpdump's: Good1 is the server-side tcpdump of a good session ("good" meaning no RST was generated). Good3 is another sever-side tcpdump of a good session. (The difference between Good1 and Good3 is the order in which ACK's were sent from the server to the client, ACK'ing the client's request. The client's request arives in 2 segements (specifically: one for the http headers, and another for a body containing an empty json object, "{}"). In Good1, the server ACK's both request segments, using 2 ACK segments, after the second request has arrived. In Good3, the server ACK's each request segment with an ACK segment as soon as the request segment arrives. Not that it should make a difference.) Bad1 is a dump, both client- and server-side, of a bad session. Bad2 is another bad session, this time server-side only. Note that in all "bad" sessions, the server ACK's each request segments immediately after having received it. I've looked at a few other bad sessions, and the situation is the same in all of them. But this is also the behavior in "Good3", so I don't see how that observation helps me, of for that matter why it should matter. I can't find any difference between good and bad sessions, or at least one that I think should matter. My question is: why are those RST's being generated? Or at least: how do I go about debugging this, or providing more info here that'll help? Edit 2 new facts that I have learned: Section 4.2.2.13 of the RFC (1122) (and Wikipedia, in the article "TCP", under "Connection Termination") says that a TCP application on one host may close the connection before it has read all of the data in its socket buffer, and in such a case the TCP on the host will sent a RST to the other side, to let it know that not all the data it has sent has been read. I'm not sure I completely understand this, since closing my side of the connection still allows me to read, no? It also means that I can't write any more. I am not sure this is relevant, though, since I see a RST after FIN. There are multiple complaints of this happening with wsgiref (Python's dev-mode HTTP server), which is exactly what I'm using. I'll keep updating as I find out more. Thanks! ~~~~~~~~~~~~~~~~~~~~ Good1 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:02.308319 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [S], seq 94268074, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943308864 ecr 0,sackOK,eol], length 0 13:28:02.308336 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [S.], seq 1726304574, ack 94268075, win 14480, options [mss 1460,sackOK,TS val 326480982 ecr 943308864,nop,wscale 3], length 0 13:28:02.309750 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943308865 ecr 326480982], length 0 13:28:02.310744 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943308865 ecr 326480982], length 350 13:28:02.310766 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943308865 ecr 326480982], length 2 13:28:02.310841 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480983 ecr 943308865], length 0 13:28:02.310918 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480983 ecr 943308865], length 0 13:28:02.315931 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480984 ecr 943308865], length 17 13:28:02.316107 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480984 ecr 943308865], length 666 13:28:02.317651 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943308872 ecr 326480984], length 0 13:28:02.318288 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943308872 ecr 326480984], length 0 13:28:02.318640 IP 192.168.1.51.51479 > 192.168.1.132.5000: Flags [F.], seq 353, ack 685, win 8192, options [nop,nop,TS val 943308872 ecr 326480984], length 0 13:28:02.318651 IP 192.168.1.132.5000 > 192.168.1.51.51479: Flags [.], ack 354, win 1944, options [nop,nop,TS val 326480985 ecr 943308872], length 0 ~~~~~~~~~~~~~~~~~~~~ Good3 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:03.311143 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [S], seq 1982901126, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943309853 ecr 0,sackOK,eol], length 0 13:28:03.311155 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [S.], seq 2245063571, ack 1982901127, win 14480, options [mss 1460,sackOK,TS val 326481233 ecr 943309853,nop,wscale 3], length 0 13:28:03.312671 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943309854 ecr 326481233], length 0 13:28:03.313330 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943309855 ecr 326481233], length 350 13:28:03.313337 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326481234 ecr 943309855], length 0 13:28:03.313342 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943309855 ecr 326481233], length 2 13:28:03.313346 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326481234 ecr 943309855], length 0 13:28:03.327942 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326481237 ecr 943309855], length 17 13:28:03.328253 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326481237 ecr 943309855], length 666 13:28:03.329076 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943309868 ecr 326481237], length 0 13:28:03.329688 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943309868 ecr 326481237], length 0 13:28:03.330361 IP 192.168.1.51.51486 > 192.168.1.132.5000: Flags [F.], seq 353, ack 685, win 8192, options [nop,nop,TS val 943309869 ecr 326481237], length 0 13:28:03.330370 IP 192.168.1.132.5000 > 192.168.1.51.51486: Flags [.], ack 354, win 1944, options [nop,nop,TS val 326481238 ecr 943309869], length 0 ~~~~~~~~~~~~~~~~~~~~ Bad1 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:01.311876 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [S], seq 920400580, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943307883 ecr 0,sackOK,eol], length 0 13:28:01.311896 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [S.], seq 3103085782, ack 920400581, win 14480, options [mss 1460,sackOK,TS val 326480733 ecr 943307883,nop,wscale 3], length 0 13:28:01.313509 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943307884 ecr 326480733], length 0 13:28:01.315614 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 350 13:28:01.315727 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:01.316229 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 2 13:28:01.316242 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:01.321019 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480735 ecr 943307886], length 17 13:28:01.321294 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 666 13:28:01.321386 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R.], seq 685, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 0 13:28:01.322727 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943307891 ecr 326480735], length 0 13:28:01.322733 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103085800, win 0, length 0 13:28:01.323221 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943307892 ecr 326480736], length 0 13:28:01.323231 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103086467, win 0, length 0 ~~~~~~~~~~~~~~~~~~~~ Bad1 -- Client Side ~~~~~~~~~~~~~~~~~~~~ 13:28:11.374654 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [S], seq 920400580, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943307883 ecr 0,sackOK,eol], length 0 13:28:11.375764 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [S.], seq 3103085782, ack 920400581, win 14480, options [mss 1460,sackOK,TS val 326480733 ecr 943307883,nop,wscale 3], length 0 13:28:11.376352 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943307884 ecr 326480733], length 0 13:28:11.378252 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 350 13:28:11.379027 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943307886 ecr 326480733], length 2 13:28:11.379732 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:11.380592 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480734 ecr 943307886], length 0 13:28:11.384968 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480735 ecr 943307886], length 17 13:28:11.385044 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943307891 ecr 326480735], length 0 13:28:11.385586 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 666 13:28:11.385743 IP 192.168.1.51.51472 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943307892 ecr 326480736], length 0 13:28:11.385966 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R.], seq 685, ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307886], length 0 13:28:11.387343 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103085800, win 0, length 0 13:28:11.387344 IP 192.168.1.132.5000 > 192.168.1.51.51472: Flags [R], seq 3103086467, win 0, length 0 ~~~~~~~~~~~~~~~~~~~~ Bad2 -- Server Side ~~~~~~~~~~~~~~~~~~~~ 13:28:01.319185 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [S], seq 1631526992, win 65535, options [mss 1460,nop,wscale 4,nop,nop,TS val 943307889 ecr 0,sackOK,eol], length 0 13:28:01.319197 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [S.], seq 2524685719, ack 1631526993, win 14480, options [mss 1460,sackOK,TS val 326480735 ecr 943307889,nop,wscale 3], length 0 13:28:01.320692 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [.], ack 1, win 8235, options [nop,nop,TS val 943307890 ecr 326480735], length 0 13:28:01.322219 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [P.], seq 1:351, ack 1, win 8235, options [nop,nop,TS val 943307890 ecr 326480735], length 350 13:28:01.322336 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [.], ack 351, win 1944, options [nop,nop,TS val 326480736 ecr 943307890], length 0 13:28:01.322689 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [P.], seq 351:353, ack 1, win 8235, options [nop,nop,TS val 943307890 ecr 326480735], length 2 13:28:01.322700 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [.], ack 353, win 1944, options [nop,nop,TS val 326480736 ecr 943307890], length 0 13:28:01.326307 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [P.], seq 1:18, ack 353, win 1944, options [nop,nop,TS val 326480737 ecr 943307890], length 17 13:28:01.326614 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [FP.], seq 18:684, ack 353, win 1944, options [nop,nop,TS val 326480737 ecr 943307890], length 666 13:28:01.326710 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [R.], seq 685, ack 353, win 1944, options [nop,nop,TS val 326480737 ecr 943307890], length 0 13:28:01.328499 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [.], ack 18, win 8234, options [nop,nop,TS val 943307896 ecr 326480737], length 0 13:28:01.328509 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [R], seq 2524685737, win 0, length 0 13:28:01.328514 IP 192.168.1.51.51473 > 192.168.1.132.5000: Flags [.], ack 685, win 8192, options [nop,nop,TS val 943307896 ecr 326480737], length 0 13:28:01.328517 IP 192.168.1.132.5000 > 192.168.1.51.51473: Flags [R], seq 2524686404, win 0, length 0

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  • TCP Zero Window with no corresponding Window Update

    - by Gandalf
    I am trying to debug a network issue and am using Wireshark and tcpdump to grab packets from my server. I have one client application that is grabbing all my available connections and then holding them, trying to send A LOT of data and essentially causing an unintentional DOS attack. While debugging I notice that I see my server sending "Window Closed" and "Zero Window" TCP packets - but never sending any "Window Update" packets. I am guessing this is why the client never lets go of the connections (it still has more data to send and is waiting). Has anyone ever seen this type of behavior before? Let's not get into the reasons why I haven't set up an iptables rule to limit concurrent connections (yeah I know). I also recently changed the MTU from 1500 to 9000 - could this have such a negative effect? (Linux) Thanks.

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  • Duplicate incoming TCP traffic on Debian Squeeze

    - by Erwan Queffélec
    I have to test a homebrew server that accepts a lot of incoming TCP traffic on a single port. The protocol is homebrew as well. For testing purposes, I'd like to send this traffic both : - to the production server (say, listening on port 12345) - to the test server (say, listening on port 23456) My clients apps are "dumb" : they never read data back, and the server never replies anyway, my server only accepts connections, and do statistical computations and store/forward/service both raw and computed data. Actually, client apps and hardware are so simple there is no way I can tell clients to send their stream on both servers... And using "fake" clients is not good enough. What could be the simplest solution ? I can of course write an intermediary app that just copy incoming data and send it back to the testing server, pretending to be the client. I have a single server running Squeeze and have total control over it. Thanks in advance for your replies.

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  • AIX network parameters to close TCP sockets of unplugged devices

    - by ADD Geek
    Hi there We have an AIX box, running what we call in banking "ATM Switch" not the ATM networking switch, but the bank ATM driver. where we have some ATM machines connected to two server processes. The problem is, when we disconnect any of these machines, the netstat -na| grep <port number> command shows that the socket established for this disconnected device is still established, we have to manually send a command from the software to make the socket aware that it is not live anymore. Is there a parameter on tcp level to make this connection aware within a minute or two that this device is not connected anymore? we had the following parameters set with root privileges: no -o tcp_keepidle=1000 no -o tcp_keepcnt=2 no -o tcp_keepintvl=150 no -o tcp_finwait2=100 it was originally having the default values. but even after we changed these parameters and restarted the server processes, the problem was still there.

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  • TCP Proxy on windows supporting SOCK5

    - by acidzombie24
    I been using privoxy just fine for the moment. However now i need to redirect non http traffic through a proxy that supports SOCK5. I looked at RINETD and spent some time googling (which led me to a SF question suggesting RINETD) but i couldnt figure out how to make it work. Specifically how to give it a listening port for my .NET apps to connect to and the SOCK5 proxy addr/port to connect to (.NET does not support using SOCK5 which is why i need a proxy). What is a simple to use proxy on windows? It must support TCP traffic (instead of only http) and supports SOCK5. -edit- portable solution preferred. I should be able to run it on my usb stick under a limited user.

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  • TCP failure on Solaris

    - by anurag kohli
    Hi All, I recently ran into a problem where a Solaris server could not establish a TCP socket on port 2126. From a packet capture I see this (note: A is a Solaris server, B is a router): A sends SYN to B B sends SYN, ACK to A Notice A (Solaris) does not acknowledge the SYN from B. Due to the business impact of the problem, I had to reboot the server to fix the problem. That said, I want to know the next time the problem occurs, what can I do to get a root cause (ie before server reboot)? Thanks in advance.

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  • Several Server Errors (No database connect, can't create TCP/IP socket etc

    - by Tobias Baumeister
    My server stops taking requests on my website today. It works for some time, but then the server just stops working and throws several errors: 500 Internal Server Error Warning: mysql_connect(): Can't create TCP/IP socket (105) in [...] on line 7 Couldn't connect to database. Please try again. mysql_connect(): Host [...] is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts' mod_fcgid: can't apply process slot for /var/www/cgi-bin/cgi_wrapper/cgi_wrapper (this is from Error Log) Any ideas what might cause it? operating system is Ubuntu

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  • How to config DNS onto TCP from UDP

    - by Dante Jiang
    Google DNS (8.8.8.8 and 8.8.4.4) are blocked (or polluted) by all ISPs available to me (and DNS by ISPs just return wrong answers for some sensitive sites!!), and it is said that if we change DNS from UDP onto TCP, the problem can be temporarily solved. My question is: how to config that on Windows 7? The solution provided by the original post: Windows 7 Ultimate DnsApi.dll v6.1.7601.17570 .text:6DC08FC8 8B 46 10 mov eax, [esi+10h] .text:6DC08FCB 89 45 F4 mov [ebp+var_C], eax var_C - 2 85A0: 90 90 90 90 90 -> 33 C0 40 EB 25 85C8: 8B 46 10 -> EB D6 40 I have not figure out how the original solution works so far. It needs to modify the .dll file, and the post provides a .dll after modification. However, I wish there was a solution without this kind of hacking.

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  • Which TCP ports to use?

    - by rowatt
    Is there a TCP port range which I can be sure will not be used by anything else for traffic between two machines? If I am reading RFC6335 correctly, I can be sure that no other applications will use specific ports in the Dynamic/Private/Ephemeral range of 49152-65535. However, if I understand correctly, it also states (section 8.1.2) that an application shouldn't assume that any given port in that range is available at any given time, which would mean I can't be 100% sure that it will be unused all the time. Specifically, I want to assign specific SSH traffic to a different port for the security benefit and so I can classify it differently for QoS purposes, and not have to worry about changing the port in the future.

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  • TCP handshake ok, then the client isn't receiving any packets from the server

    - by infgeoax
    Topology: Client ----- Intermediate Device ----- Server Client: win7 Intermediate Device: unknown Server: CentOS 5.8 The problem occurs when the client and server are trying to establish a SSL connection. It happens to one specific port, 2000. I haven't been able to replicate the problem with other port numbers. I captured packets on both client and server. After the TCP handshake, from the client's perspective, it's not receiving ACKs for its previously sent packets so it kept re-sending them. On the server side, however, it did receive those packets and sent ACK packets. The weird thing is, after the server sent those ACKs, it received a [RST, ACK] packet, from the intermediate device, for every packet it sent. What could be the cause?

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  • Relation between TCP/IP Keep Alive and HTTP Keep Alive timeout values

    - by Suresh Kumar
    I am trying to understand the relation between TCP/IP and HTTP timeout values. Are these two timeout values different or same? Most Web servers allow users to set the HTTP Keep Alive timeout value through some configuration. How is this value used by the Web servers? is this value just set on the underlying TCP/IP socket i.e is the HTTP Keep Alive timeout and TCP/IP Keep Alive Timeout same? or are they treated differently? My understanding is (maybe incorrect): The Web server uses the default timeout on the underlying TCP socket (i.e. indefinite) and creates Worker thread that counts down the specified HTTP timeout interval. When the Worker thread hits zero, it closes the connection.

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  • tcp connect hangs on SYN_SENT if something listens, gets CONN_REFUSED if nothing listens

    - by Amos Shapira
    I'm hitting a very strange problem - when I try to connect to one of our servers the client hangs with SYN_SENT if something listens on the port (e.g. Apache on port 80, sshd on port 22 or SMTP on port 25) but if I try to connect to a port on which nothing listens then I immediately get a "CONNECTION refused" error. Connecting to other applications (e.g. rsyncd on some arbitrary port) succeeds. I ran tcpdump on the server and see that the SYN packets arrive to it but it only sends a response if nothing listens on that port. e.g.: on the server I run: # tcpdump -nn port 81 06:49:34.641080 IP 10.x.y.z.49829 server.81: S 3966400723:3966400723(0) win 12320 06:49:34.641118 IP server.81 x.y.z.49829: R 0:0(0) ack 3966400724 win 0 But if I listen on this port, e.g. with nc -4lvvv 81 & Then the output of tcpdump is: 06:44:31.063614 IP x.y.z.45954 server.81: S 3493682313:3493682313(0) win 12320 (and repeats until I stop it) The server is CentOS 5, the client is Ubuntu 11.04, the connection is done between two LAN's over per-user TCP OpenVPN. Connection to other servers on that network do not have a problem. Connecting from the other servers on the same network to that server works fine. Connections from other clients in our office over openvpn is also not a problem. What am I missing? Thanks.

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  • Real benefits of tcp TIME-WAIT and implications in production environment

    - by user64204
    SOME THEORY I've been doing some reading on tcp TIME-WAIT (here and there) and what I read is that it's a value set to 2 x MSL (maximum segment life) which keeps a connection in the "connection table" for a while to guarantee that, "before your allowed to create a connection with the same tuple, all the packets belonging to previous incarnations of that tuple will be dead". Since segments received (apart from SYN under specific circumstances) while a connection is either in TIME-WAIT or no longer existing would be discarded, why not close the connection right away? Q1: Is it because there is less processing involved in dealing with segments from old connections and less processing to create a new connection on the same tuple when in TIME-WAIT (i.e. are there performance benefits)? If the above explanation doesn't stand, the only reason I see the TIME-WAIT being useful would be if a client sends a SYN for a connection before it sends remaining segments for an old connection on the same tuple in which case the receiver would re-open the connection but then get bad segments and and would have to terminate it. Q2: Is this analysis correct? Q3: Are there other benefits to using TIME-WAIT? SOME PRACTICE I've been looking at the munin graphs on a production server that I administrate. Here is one: As you can see there are more connections in TIME-WAIT than ESTABLISHED, around twice as many most of the time, on some occasions four times as many. Q4: Does this have an impact on performance? Q5: If so, is it wise/recommended to reduce the TIME-WAIT value (and what to)? Q6: Is this ratio of TIME-WAIT / ESTABLISHED connections normal? Could this be related to malicious connection attempts?

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  • Close TCP connection when owner process is already killed

    - by Otiel
    I have a Windows service that - when it starts - opens some WCF services to listen on the 8000 port. It happens that this service crashes sometimes. When it does, the TCP connection is not released, thus causing my service to throw an exception if I try to start it again: AddressAlreadyInUseException: There is already a listener on IP endpoint 0.0.0.0:8000 Some observations: When running CurrPorts or netstat -ano, I can see that the 8000 port is still in use (in LISTENING state) and is owned by the Process ID XXX that corresponded to my service process ID. But my service has already crashed, and does not appear in the Task Manager anymore. Thus I can't kill the process to free the port! Of course, running taskkill /PID XXX returns: ERROR: The process "XXX" not found. When running CurrPorts or netstat -b, I can see that the process name involved in creating the listening port is System, and not as MyService.exe (whereas it is MyService.exe when my service is running). I tried to use CurrPorts to close the connection, but I always get the following error message: Failed to close one or more TCP connections. Be aware that you must run this tool as admin in order to close TCP connections. (Useless to say, I do run CurrPorts as Administrator...) TCPView is not much help either: the process name associated to the 8000 port is <non-existent>, and doing "End process" or "Close connection" has no effect. I tried to see if there was not a child process associated with the PID XXX using Process Explorer, but no luck here. If I close my service properly (before it crashes), the TCP connection is correctly released. This is normal, as I close the WCF service hosts in the OnStop() event of my service. The only way I found to release the connection is to restart the server (which is not convenient in a production environment as you can guess). Waiting does not help, the TCP connection is never released. How can I close the connection without restarting the Windows server? PS: found some questions extremely similar to mine.

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