How does one attain 1,000+ connections like blockchain.info?

Question

At this moment, blockchain.info has over 1,900 nodes connected to their bitcoin client.

I have been running an m1.small ubuntu 12.04 server and bitcoind for ~4 days straight now with no reboots. My bitcoind client still only shows ~60 connections maximum when performing a "./bitcoind getinfo" command.

How can I achieve 1,000+ connections to my bitcoind client? And is it "worth it" in your opinion?

EDIT: I have re-started my bitcoind client with the -maxconnections=1000 and -timeout=15000 parameters but after ~12 hours of running bitcoind, the number of connections is only up to ~40. And I don't seem to be maxing out my CPU, RAM, or bandwidth just yet.

EDIT 2: I have not seen a "connected time" over 8 hours in the list provided by blockchain.info so that tells me they must restart their server every 8 hours or so. Either that, or connections drop and refresh after 8 hours? I am beginning to think that blockchain.info keeps track of IP addresses running bitcoin in a database of sorts... and forefully connects to them every time their bitcoind reboots. Am I right?

Answer 1

The bitcoind client has a maxconnections configuration option. The client launched With -maxconnections=N will allow up to N incoming connections to be established simultaneously.

Perhaps you may need to increase the connection timeout for that many connection attempts from a single (possibly underpowered) node. Perhaps set it to like 15 seconds (15000 ms).

-timeout= Specify connection timeout in milliseconds (default: 5000)

[Edit: Pieter Wuille's answer gets you further there. -addnode will let you force new outgoing conections to nodes when you have their IP addresses.]

Answer 2

Bitcoin by default will not make more than 8 outgoing connections, and -maxconnections only controls how many incoming connections you allow. Feel free to set this higher, but it will take time before others connect to you in large numbers.

Please don't change this, as there is no need. Connectable peers on the network are a scarce resource, and essential to the decentralization. If people go try connect to all of them like some sites do, we'll very quickly run out.

In case you're a merchant or miner, you perhaps want to set up a few fixed connections to trusted others (see the -addnode command line/config option), but having more connections does not mean stronger verification (the reference client always verifies everything) or even faster relaying (as you'll slow down by distributing new blocks and transactions to all your peers). It is mostly a matter of providing a service to the network.

Answer 3

The given answers don't answer the question. Even though it might not makes sense to achieve a thousand connections, here's how to do that on Debian. You want to make some slightly changes in the code and recompile bitcoind:

Get required packages for compiling:

$ aptitude install git make build-essential libssl-dev libboost-all-dev libdb-dev libdb++-dev libminiupnpc-dev

Clone the git repository (make sure the version is the most recent branch):

$ cd /usr/src
$ sudo git clone -b 0.8.4 https://github.com/bitcoin/bitcoin
$ cd bitcoin/src

Edit the net.cpp file:

@@ -27,7 +27,7 @@
 using namespace std;
 using namespace boost;

-static const int MAX_OUTBOUND_CONNECTIONS = 8;
+static const int MAX_OUTBOUND_CONNECTIONS = 1000;

 bool OpenNetworkConnection(const CAddress& addrConnect, CSemaphoreGrant *grantOutbound = NULL, const char *strDest = NULL, bool fOneShot = false);

@@ -1533,7 +1533,7 @@
             OpenNetworkConnection(CAddress(vserv[i % vserv.size()]), &grant);
             MilliSleep(500);
         }
-        MilliSleep(120000); // Retry every 2 minutes
+        MilliSleep(5000); // Retry every 5 seconds
     }
 }

1.) By changing MAX_OUTBOUND_CONNECTIONS, the client will go on connecting until it reaches 1000 proactive connections.

2.) By changing the sleep timeout new connections are tried more frequently.

Compile and install bitcoind:

$ sudo make -f makefile.unix
$ sudo mv bitcoind /usr/bin

Don't forget to set the maxconnections in bitcoin.conf:

maxconnections=1000

Start bitcoind and your done. The client will make lots of connections really fast.

Disclaimer: As Pieter Wuille pointed out, it can harm the network to run a modified client like this one. Please use this solution for research purposes only and not as a permanent solution.

Answer 4

As nobody seems to have mentioned it I'll chip in for future reference. If your bitcoind node is behind a router/NAT then you can only connect to others, they cannot connect to you. Let's assume most people are in that situation, which makes most nodes unconnectable (directly at least). If you open up your node port on your router then every bitcoind node out there will be able to connect to you if they wish rather than your node only being able to connect to others who have opened their port. The same applies to Bittorrent and other p2p systems.

Answer 5

Why do you need 1,000+ connections?

By default bitcoind cannot have more than 125 connections. You need to start bitcoind with the parameter -maxconnections=<n> or set maxconnections=<n> in bitcoin.conf to be able to connect to more peers.

Answer 6

To check whether you allow incoming, use this: https://bitnodes.21.co There is a button to check your ip and if it results in green, you are fine to have incoming connection. Once you have that, I was told you can have more outgoing connection. Good luck.