Connecting client socket to server socket only once in socket programming

srinietrx · 08-14-2017, 02:55 AM

I am trying to connect client socket to server socket only once when program starts. After that it should only send and receive.

Also I written this client program inside my server socket.Since my requirement is my server will receive some data from original client and send same data(as client) to another server and receive from server and send same data to original client

Three things are
1. Original client(Some device which act as client you can say)
2. Server(which also contains client like program in thread to send and receive)
3. External Server( Which I will hit from second step)

The code I am having for second step is shown below link.
https://pastebin.com/UmPQJ70w

My question is more related to C++ Where exactly I need to put below code in program.

Code:

 TCPConnector* connector_client = new TCPConnector();
        printf("ip_client = %s\tport_client = %s\tport_client_int = %d\n", ip_client.c_str(), port_client.c_str(),atoi(port_client.c_str()));
        TCPStream* stream_client = connector_client->connect(ip_client.c_str(), atoi(port_client.c_str()));

-- If I am writing inside While loop it works but it connect every time.
-- If I write outside for loop as shown in paste bin. It works only one time after that due to delete stream_client; as shown below in code. If I remove delete stream_client it works but memory will not free.

Code:

-------
-------
--------
len = stream_client->receive(line, sizeof(line));
line[len] = NULL;
printf("received - %s\n", line);
delete stream_client;

So what is the smartest way I can handle in my application.

NevemTeve · 08-14-2017, 04:57 AM

This thing is called 'proxy'. Here is two way you could choose:

1. for every incoming connection create an outgoing connection -- that's how rinetd works.

2. share one (or a few) outgoing connection between more incoming connection, if the protocol allows that. (cf: multiplexing)

srinietrx · 08-16-2017, 06:37 AM

Hi Nevem,

I found point no.2 useful for my project.Is there is any sample code to perform this or any document I can refer.

NevemTeve · 08-17-2017, 04:09 AM

You should store the data of your outgoing connections, sg like this:

Code:

typedef struct OutConnData {
    int state;        /* -1/0/1 = unused/free/in-use */
    int sockethandle; /* -1 if unused */
    ...
} OutConnData;

typedef struct OutConnData_Collection {
    OutConnData *ptr; /* pointer to n_allocated elements */
    int n_allocated;
    int n_unsed;
    int n_free;
} OutConnData_Collection;

from now on it is easy: you only have to write the operations of these structures

srinietrx · 08-19-2017, 12:18 AM

Hi Nevem,
Thanks for giving few inputs.
After doing little bit research I found rinetd can solve problem without writing any extra code(but keeping my original code as option for time being). I am facing two problems.
==>Question 1
I am running server socket program in one computer ./server_local 5000 192.168.1.7 and hitting from client ./client_local 5000 192.168.1.7

and made configuration in /etc/rinetd.conf

PHP Code:



#bind address    bindport     connectaddress   connectport
192.168.1.7       5000        202.52.134.163    5010

rinetd restared.
and running remote server socket in ./server_remote 1 5010 10.2.4.102. So from any client program if hit giving ip address as 202.52.134.163 and port number 5010 I am able to send data to this server.

Now when I hit from client_local to server_local I am thinking rinetd will redirect from (192.168.1.7:5000) to 202.52.134.163:5010 and get data in this server. But it is not happening. Is my understanding of rinetd wrong or any configuration issue.
Note:- Pardon me for asking networking related question in programming forum.Since it is related to original question not opening new thread

==> Question 2:-
My aim is to do connection only once i.e TCP connection should be established only once after that send receive should happen .Whether rinetd solve this problem. Because my remote server connects only once and if we try to connect in parallel many connection shows connection refused.
I tried to read documents regarding this but not getting exact solution. So I am trying to work on working example as mentioned in Question 1

NevemTeve · 08-20-2017, 11:53 AM

I don't really get your example. Let's assume you have three computers, A, B, and C, with the following IP-addresses:

Code:

1.1.1.1 A
2.2.2.2 B
3.3.3.3 C

Now let A be the client, B the proxy, C the server (port 3333). You should run rinetd on B, with the following parameters:

Code:

# host_B:/etc/rinetd.conf
#bind_address bindport connect_address connect_port
2.2.2.2       4444     3.3.3.3         3333

Now the client on 'A' can connect to 'B' (i.e. 2.2.2.2:4444), and it will be forwarded to 'C' (i.e. 3.3.3.3:3333)