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• How do you interface with a USB to Parallel adapter?

  - by Hans

  I'm currently doing a project where I have to interact with a circuit I made through the parallel port of a computer. However, my computer doesn't have a parallel port so I borrowed a Parallel to USB adapter cable. The cable didn't come with any drivers, but it's recognized by the device manager as a "USB Printing Support" controller, under the USB section. It seems that old parallel printers can be plugged in and work properly without any problems. So my question is, if I write a program in Java that tries to interact with a parallel port directly, will it work? And if not, can anyone give me some pointers as to what I need to do to interact with it? Thanks.

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• PostgreSQL JOIN with array type with array elements order, how to implement?

  - by Adiasz

  Hello I have two tables in database: CREATE TABLE items( id SERIAL PRIMARy KEY, ... some other fields ); This table contains come data row with unique ID. CREATE TABLE some_choosen_data_in_order( id SERIAL PRIMARy KEY, id_items INTEGER[], ); This table contains array type field. Each row contains values of IDs from table "items" in specyfic order. For example: {2,4,233,5}. Now, I want to get data from table "items" for choosen row from table "some_choosen_data_in_order" with order for elements in array type. The my attempt is JOIN: SELECT I.* FROM items AS I JOIN some_choosen_data_in_order AS S ON I.id = ANY(S.id_items) WHERE S.id = ? Second attempt was subquery like: SELECT I.* FROM items AS I WHERE I.id = ANY (ARRAY[SELECT S.id_items FROM some_choosen_data_in_order WHERE id = ?]) But none of them keep IDs order in array field. Could You help me, how to get data from "items" table with correspond with array IDs order from "some_choosen_data_in_order" table for specyfic row?

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• Windows.Networking.EndpointPair constructor parameters

  - by ComFreek

  I want to create a new EndpointPair object: // hostname is a string // port is an integer var endpointPair = new Windows.Networking.EndpointPair(null, null, hostname, port); But I always get this error: 0x800a000d - JavaScript runtime error: Type mismatch I've already tried the following: converting port to a string passing "" instead of null for the first two Parameters. (null should be okay if the documentation here, under the section Remarks, is right) passing no Parameters, but that ends up in an "too few parameters" error message Above all, the documentation about the constructor has been removed (as of September 4, 2012): http://msdn.microsoft.com/en-us/library/windows/apps/windows.networking.endpointpair.endpointpair.aspx

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• OpenMP + SSE gives no speedup

  - by Sayan Ghosh

  Hi, My Professor found out this interesting experiment of 3D Linearly separable Kernel Convolution using SSE and OpenMP, and gave the task to me to benchmark the statistics on our system. The author claims a crazy 18 fold speedup from the serial approach! Might not be always, but we were expecting at least a 2-4 times speedup running this on a Dual Core Intel. http://software.intel.com/en-us/articles/16bit-3d-convolution-sse4openmp-implementation-on-penryn-cpu/#comment-41994 Alas, we could find exactly no speedup. The serial code performs always better, with or without OpenMP. I am using Linux, and observed a certain trend...when no other processes are running on the system, after a while the loadavg starts increasing, and the the %CPU utilization falls down. Another probable false positive which I ran into accidentally...I started the program, then immediately paused it. Then I ran it on background with bg, and saw a speedup of more than 2. This happens all the time! Any advice would be great. Thanks, Sayan

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• How to make socket.listen(1) work for some time and then continue rest of code???

  - by Rami Jarrar

  I'm making server that make a tcp socket and work over port range, with each port it will listen on that port for some time, then continue the rest of the code. like this:: import socket sck = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sck.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) msg ='' ports = [x for x in xrange(4000)] while True: try: for i in ports: sck.bind(('',i)) ## sck.listen(1) ## make it just for some time and then continue this ## if there a connection do this conn, addr = sck.accept() msg = conn.recv(2048) ## do something ##if no connection continue the for loop conn.close() except KeyboardInterrupt: exit() so how i could make sck.listen(1) work just for some time ??

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• Pattern for managing reference count and object life

  - by Gopalakrishnan Subramani

  We have a serial port which is connected to hundreds of physical devices on the same wire. We have protocols like Modbus and Hart to handle the request and response between the application and devices. The question is related to managing the reference count of the channel. When no device is using the channel, the channel should be closed. public class SerialPortChannel { int refCount = 0; public void AddReference() { refCount++; } public void ReleaseReference() { refCount--; if (refCount <= 0) this.ReleasePort(); //This close the serial port } } For each device connected, we create a object for the device like device = new Device(); device.Attach(channel); //this calls channel.AddReference() When the device disconnect, device.Detach(channel); //this calls channel.ReleaseReference() I am not convinced by the reference count model. Are there any better way to handle this problem in .NET World?

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• Accurate Timings with Oscilloscopes on PC

  - by Paul Bullough

  In the world of embedded software (firmware) it is fairly common to observe the order of events, take timings and optimise a program by getting it to waggle PIO lines and capturing their behavior on an oscilloscope. In days gone by it was possible to toggle pins on the serial and parallel ports to achieve much the same thing on PC-based software. This made it possible to capture host PC-based software events and firmware events on the same trace and examine host software/firmware interactions. Now, my new laptop ... no serial or parallel ports! This is increasingly the case. So, does anyone have any suggestions as to go about emitting accurate timing signals off a "modern" PC? It strikes me that we don't have any immediately programmable, lag-free output pins left. The solution needs to run off a laptop, so using add-on cards that only plug into desktops are not permitted.

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• How could I get informations about the SIM card on Windows CE

  - by jeleb

  Hello, I am using a device running on WindowsCE 5.00. I cannot connect the GPRS, there is an error message telling that the port cannot be opened and may be in use by another application. I am not sure but I think the port it is talking about is a comp port to the SIM card that cannot be opened because the SIM doesn't work anymore. To tell the truth, it is likely that one of my coworker did lock the SIM and kept his mouth shut ... How could I get any information about the SIM on Windows CE ? I am new at this and Windows CE is not really user friendly ... I have been strongly searching this on internet but didn't find anything. Any kind of information will be welcomed. Thanks,

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• How do you set rate limit access to your API using Iptables?

  - by Cory

  How can you set rate limit access to API using Iptables. Tried to set limit using port 80, but I don't want to set limit to the web access entirely. Is there a way to specified a subdomain rather than port. Example: set rate limit to api.example.com not example.com? If there is no way to set rate limit by subdomain, what is the suggested rate limit access to port 80 without risking blocking a legitimate web user? One connection per second would be enough?

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• python and paramiko: how to check if end of ssh tunnel is still alive and reestablish if not?

  - by Christian

  Hello all, I'm trying to achieve the following: I have two hosts A and B. A establishes a remote port forwarding tunnel on B, i.e. B is the one a port is forwarded on to some where else and A is the one that sets up the tunnel. I tried the script rforward.py that ships with paramiko and it works very well so far. (I'm running rforward.py on A, which connects to B and forwards a port of B to somewhere else) However, when B is shutting down, A doesn't seem to recognize it. I'd rather like A to recognize that B is down and to try to reestablish the connection periodically in case B comes up again. Is there a way to do this? Thanks.

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• Consolidate loan, purchase & sale tables into one transaction table.

  - by Frank Computer

  INFORMIX-SE with ISQL 7.3: I have separate tables for Loan, Purchase & Sales transactions. Each tables rows are joined to their respective customer rows by: customer.id [serial] = loan.foreign_id [integer]; = purchase.foreign_id [integer]; = sale.foreign_id [integer]; I would like to consolidate the three tables into one table called "transaction", where a column: transaction.trx_type char(1) {L=Loan, P=Purchase, S=Sale} identifies the transaction type. Each transaction will be assigned a unique transaction number [serial]. Is this a good idea or is it better to keep them in separate tables? Storage space is not a concern, I think it would be easier programming & user-wise to have all types of transactions under one table, whenever possible. This implies denormalization.

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• how do I migrate Datamapper on appengine

  - by Roy

  I've changed my model from class Place include DataMapper::Resource has n, :trails property :id, Serial property :name, String, :length => 140 property :tag, String, :required => true timestamps :at end to class Place include DataMapper::Resource has n, :trails property :id, Serial property :name, String, :length => 140 property :tag, String, :required => true property :trail_count, Integer, :default => 0 timestamps :at end I just added "property :trail_count, Integer, :default = 0" and i want to migrate the existing appengine table to have the extra field "trail_count" i've read that DataMapper.auto_upgrade! should do it. but i get an error "undefined method `auto_upgrade!' for DataMapper:Module" can you please help How do i migrate the DM models?

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• Improve a haskell script

  - by Hector Villalobos

  I'm a newbie in Haskell and I'd like some opinions about improving this script. This is a code generator and requires a command line argument to generate the sql script. ./GenCode "people name:string age:integer" Code: import Data.List import System.Environment (getArgs) create_table :: String -> String create_table str = "CREATE TABLE " ++ h (words str) where h (x:xs) = let cab = x final = xs in x ++ "( " ++ create_fields xs ++ ")" create_fields (x:xs) = takeWhile (/=':') x ++ type x ++ sig where sig | length xs > 0 = "," ++ create_fields xs | otherwise = " " ++ create_fields xs create_fields [] = "" type x | isInfixOf "string" x = " CHARACTER VARYING" | isInfixOf "integer" x = " INTEGER" | isInfixOf "date" x = " DATE" | isInfixOf "serial" x = " SERIAL" | otherwise = "" main = mainWith where mainWith = do args <- getArgs case args of [] -> putStrLn $ "You need one argument" (x:xs) -> putStrLn $ (create_table x)

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• CakePHP 'Cake is NOT able to connect to the database'

  - by kand

  I've looked at this post about a similar issue: CakePHP: Can't access MySQL database and I've tried everything they mentioned in there including: Changing my database.php so that the 'port' attribute for both $default and $test are the location of my mysqld.sock file Changing the 'port' attribute to the actual integer that represents the port in my my.cnf mysql config Changing the mysql socket locations in php.ini to the location of my mysqld.sock file I'm using ubuntu 11.04, apache 2.2.17, mysql 5.1.54, and CakePHP 1.3.10. My install of mysql and apache don't seem to match any conventions, as in, all the config files are there, they are all just in really weird places--I'm not sure why that is, but I've tried reinstalling both programs multiple times with the same results... At any rate, I can log into mysql from the terminal and use it normally, and apache is working because I can see the CakePHP default homepage. I just can't get it to change the message 'Cake is NOT able to connect to the database'. SOLVED: Figured it out, had to change php.ini so that extension_dir pointed to the correct directory and had to add a line extension=mysql.so.

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• Database design - alternatives for Entity Attribute Value (AEV)

  - by Bob

  Hi, see http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters for similar topic. My question: i want to design a database, that will be used for a production facility of different types of products where each product has its own (number of) parameters. because i want the serial numbers to be in one tabel for overview purposes i have a problem with these different paraeters . One solution could be AEV, but it has its downsides, certainly because we have +- 5 products with every product +- 20.000 serial numbers (records). it looks a bit overkill to me... I just don't know how one could design a database so that you have an attribute in a mastertable that says: 'hey, you could find details of this record in THAT detail-table". 'in a way that you qould easely query the results) currenty i am using Visual Basic & Acces 2007. but i'm going to Visual Basic & MySQL. thanks for your help. Bob

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• libcurl - unable to download a file

  - by marmistrz

  I'm working on a program which will download lyrics from sites like AZLyrics. I'm using libcurl. It's my code lyricsDownloader.cpp #include "lyricsDownloader.h" #include <curl/curl.h> #include <cstring> #include <iostream> #define DEBUG 1 ///////////////////////////////////////////////////////////////////////////// size_t lyricsDownloader::write_data_to_var(char *ptr, size_t size, size_t nmemb, void *userdata) // this function is a static member function { ostringstream * stream = (ostringstream*) userdata; size_t count = size * nmemb; stream->write(ptr, count); return count; } string AZLyricsDownloader::toProviderCode() const { /*this creates an url*/ } CURLcode AZLyricsDownloader::download() { CURL * handle; CURLcode err; ostringstream buff; handle = curl_easy_init(); if (! handle) return static_cast<CURLcode>(-1); // set verbose if debug on curl_easy_setopt( handle, CURLOPT_VERBOSE, DEBUG ); curl_easy_setopt( handle, CURLOPT_URL, toProviderCode().c_str() ); // set the download url to the generated one curl_easy_setopt(handle, CURLOPT_WRITEDATA, &buff); curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, &AZLyricsDownloader::write_data_to_var); err = curl_easy_perform(handle); // The segfault should be somewhere here - after calling the function but before it ends cerr << "cleanup\n"; curl_easy_cleanup(handle); // copy the contents to text variable lyrics = buff.str(); return err; } main.cpp #include <QString> #include <QTextEdit> #include <iostream> #include "lyricsDownloader.h" int main(int argc, char *argv[]) { AZLyricsDownloader dl(argv[1], argv[2]); dl.perform(); QTextEdit qtexted(QString::fromStdString(dl.lyrics)); cout << qPrintable(qtexted.toPlainText()); return 0; } When running ./maelyrica Anthrax Madhouse I'm getting this logged from curl * About to connect() to azlyrics.com port 80 (#0) * Trying 174.142.163.250... * connected * Connected to azlyrics.com (174.142.163.250) port 80 (#0) > GET /lyrics/anthrax/madhouse.html HTTP/1.1 Host: azlyrics.com Accept: */* < HTTP/1.1 301 Moved Permanently < Server: nginx/1.0.12 < Date: Thu, 05 Jul 2012 16:59:21 GMT < Content-Type: text/html < Content-Length: 185 < Connection: keep-alive < Location: http://www.azlyrics.com/lyrics/anthrax/madhouse.html < Segmentation fault Strangely, the file is there. The same error is displayed when there's no such page (redirect to azlyrics.com mainpage) What am I doing wrong? Thanks in advance EDIT: I made the function for writing data static, but this changes nothing. Even wget seems to have problems $ wget http://www.azlyrics.com/lyrics/anthrax/madhouse.html --2012-07-06 10:36:05-- http://www.azlyrics.com/lyrics/anthrax/madhouse.html Resolving www.azlyrics.com... 174.142.163.250 Connecting to www.azlyrics.com|174.142.163.250|:80... connected. HTTP request sent, awaiting response... No data received. Retrying. Why does opening the page in a browser work and wget/curl not? EDIT2: After adding this: curl_easy_setopt(handle, CURLOPT_FOLLOWLOCATION, 1); The log is: * About to connect() to azlyrics.com port 80 (#0) * Trying 174.142.163.250... * connected * Connected to azlyrics.com (174.142.163.250) port 80 (#0) > GET /lyrics/anthrax/madhouse.html HTTP/1.1 Host: azlyrics.com Accept: */* < HTTP/1.1 301 Moved Permanently < Server: nginx/1.0.12 < Date: Fri, 06 Jul 2012 09:09:47 GMT < Content-Type: text/html < Content-Length: 185 < Connection: keep-alive < Location: http://www.azlyrics.com/lyrics/anthrax/madhouse.html < * Ignoring the response-body * Connection #0 to host azlyrics.com left intact * Issue another request to this URL: 'http://www.azlyrics.com/lyrics/anthrax/madhouse.html' * About to connect() to www.azlyrics.com port 80 (#1) * Trying 174.142.163.250... * connected * Connected to www.azlyrics.com (174.142.163.250) port 80 (#1) > GET /lyrics/anthrax/madhouse.html HTTP/1.1 Host: www.azlyrics.com Accept: */* < HTTP/1.1 200 OK < Server: nginx/1.0.12 < Date: Fri, 06 Jul 2012 09:09:47 GMT < Content-Type: text/html < Transfer-Encoding: chunked < Connection: keep-alive < Segmentation fault

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• How do i serlialize the product using php?

  - by Ibrahim Azhar Armar

  hi, i am building a real estate application where in it will store the properties and search it. the property will have different categories like (residential, commercial, industrial or agricultural). based upon the category i want to serailize each and every property listing . for example the property with id 1 belongs to resedential will have the serial code rs_SOMERANDOMUNIQUENUMBER. and for commercial it can be cm_SOMERANDOMUNIQUENUMBER and so on. for this my database table looks like this. CREATE TABLE IF NOT EXISTS `propSerials` ( `id` bigint(20) NOT NULL auto_increment, `serial` varchar(50) NOT NULL, `property_id` int(10) UNIQUE NOT NULL, PRIMARY KEY  (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; what would be the best possible format to store the serial with the prefix according to category? thank you

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• php open_socket

  - by sea_1987

  Hello, I am trying to open a socket to use with secure tradings xpay api, however when I check to see if the socket is open I get error returned, Can't assign requested address I need to open up 127.0.0.1:5000 is there something wring with my code that means I cannot do this? if (isset($xpay_port) and ($socket=socket_create(AF_INET, SOCK_STREAM, SOL_TCP)) and (socket_connect($socket, $address, $port))) { $text="Connection successful on IP $address, port $port"; socket_close($socket); } else $text="Unable to connect<pre>".socket_strerror(socket_last_error())."</pre>"; echo "<html><head></head><body>". $text. "</body></html>";

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• Ruby - model.rb:20: syntax error, unexpected keyword_end, expecting $end

  - by Yasir Adnan

  I don't understand what's wrong with my code. model.rb require 'Gemfile' DataMapper.setup(:default, 'mysql://root:password@localhost/rengine') Class User include DataMapper::Resource property :id, Serial # An auto-increment integer key property :email, String, format: :email_address property :username, String, required: true property :password, String , length: 10..255, required: true property :created_at, DateTime property :updated_at, DateTime #User can have mutiple posts has n, :posts end Class Post include DataMapper::Resource property :id, Serial # An auto-increment integer key property :title, String, required: true property :body, Text, required: true property :created_at, DateTime property :updated_at, DateTime #Posts belongs to a USer belongs_to :user end DataMapper.auto_upgrade! I didn't able to figure out. What's problem is here??

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• socket.error: [Errno 10054]

  - by C0d3r

  import socket, sys if len(sys.argv) !=3 : print "Usage: ./supabot.py <host> <port>" sys.exit(1) irc = sys.argv[1] port = int(sys.argv[2]) sck = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sck.connect((irc, port)) sck.send('NICK supaBOT\r\n') sck.send('USER supaBOT supaBOT supaBOT :supaBOT Script\r\n') sck.send('JOIN #darkunderground' + '\r\n') data = '' while True: data = sck.recv(1024) if data.find('PING') != -1: sck.send('PONG ' + data.split() [1] + '\r\n') print data elif data.find('!info') != -1: sck.send('PRIVMSG #darkunderground supaBOT v1.0 by sourD' + '\r\n') print sck.recv(1024) when I run this code I get this error.. socket.error: [Errno 10054] An existing connection was forcibly closed by the remote host it says that the error is in line 16, in data = sck.recv(1024)

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• Licensing c program

  - by Daniel

  Hi, How would i licence my c command line program, e.g limited functionality without a serial number?

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• Communication via internet in Java

  - by Stuart

  What I mean is like servers on video games. You can run an application and it will set up a server on your computer with an IP and a port. For example, how would you make an application where one host application sets up a thing where it has an IP and a port, and another computer that has access to the internet as well can type in the IP and port and it would be able to communicate with the host? I mean simple communication, like sending a boolean or String. And would there be any security problems that would be needed to fix?

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• Postgresql count+sort performance

  - by invictus

  I have built a small inventory system using postgresql and psycopg2. Everything works great, except, when I want to create aggregated summaries/reports of the content, I get really bad performance due to count()'ing and sorting. The DB schema is as follows: CREATE TABLE hosts ( id SERIAL PRIMARY KEY, name VARCHAR(255) ); CREATE TABLE items ( id SERIAL PRIMARY KEY, description TEXT ); CREATE TABLE host_item ( id SERIAL PRIMARY KEY, host INTEGER REFERENCES hosts(id) ON DELETE CASCADE ON UPDATE CASCADE, item INTEGER REFERENCES items(id) ON DELETE CASCADE ON UPDATE CASCADE ); There are some other fields as well, but those are not relevant. I want to extract 2 different reports: - List of all hosts with the number of items per, ordered from highest to lowest count - List of all items with the number of hosts per, ordered from highest to lowest count I have used 2 queries for the purpose: Items with host count: SELECT i.id, i.description, COUNT(hi.id) AS count FROM items AS i LEFT JOIN host_item AS hi ON (i.id=hi.item) GROUP BY i.id ORDER BY count DESC LIMIT 10; Hosts with item count: SELECT h.id, h.name, COUNT(hi.id) AS count FROM hosts AS h LEFT JOIN host_item AS hi ON (h.id=hi.host) GROUP BY h.id ORDER BY count DESC LIMIT 10; Problem is: the queries runs for 5-6 seconds before returning any data. As this is a web based application, 6 seconds are just not acceptable. The database is heavily populated with approximately 50k hosts, 1000 items and 400 000 host/items relations, and will likely increase significantly when (or perhaps if) the application will be used. After playing around, I found that by removing the "ORDER BY count DESC" part, both queries would execute instantly without any delay whatsoever (less than 20ms to finish the queries). Is there any way I can optimize these queries so that I can get the result sorted without the delay? I was trying different indexes, but seeing as the count is computed it is possible to utilize an index for this. I have read that count()'ing in postgresql is slow, but its the sorting that are causing me problems... My current workaround is to run the queries above as an hourly job, putting the result into a new table with an index on the count column for quick lookup. I use Postgresql 9.2.

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• Saving a 'Date' using DataMapper on AppEngine+JRuby

  - by Ryan Montgomery

  I have a a model as follows: class Total include DataMapper::Resource property :id, Serial property :amount, Float, :default => 0.00 property :day, Date belongs_to :calendar end I am trying to select a specific Total from the data-store. class Calendar include DataMapper::Resource property :id, Serial property :name, String has n, :totals def get_total_for(date) return Total.first(:day => date, :calendar => self) end end When I call get_total_for(DateTime.now) I receive the following error on the call to the data-store. java.lang.IllegalArgumentException: day: org.jruby.RubyObject is not a supported property type. Is Date not allowed for usage in AppEngine? Is this a DataMapper issue? I have tried changing the name of the :day property to something else (hoping it was just a name conflict) but it doesn't seem to matter. Thanks for any help you can provide.

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• Android Source code download error

  - by user351850

  Hi all I have followed the instructions on the Android website on how to download the latest android source code files but it gives errors when i run this command: repo init -u git://android2.git.kernel.org/platform/manifest.git It gives the following error: Getting repo ... from git://android.git.kernel.org/tools/repo.git android.git.kernel.org[0: 199.6.1.176]: errno=Connection refused android.git.kernel.org[0: 130.239.17.12]: errno=Connection refused fatal: unable to connect a socket (Connection refused) On checking forums for its resolution, i was told that port 9418 was being blocked. I use Ubuntu 10.04 and ensured that the firewall wasnt blocking the port and also enabled the port and the above IP addresses. I also spoke to the networking peeps who ensured that no traffic from the internet is being blocked. I would be glad if i could get directions on how to proceed next. Many thanks as you respond. Saheed.

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