Connecting & Reading to a TCP/IP socket from a different ROS Node

edit

Hi Friends,

I am using TCP/IP protocol for one of my application, in which I am creating a TCP/IP socket to Transmit/Receive data from/to the Server (a different PC).

My system is the Client in which I have created two ROS nodes (say A & B),

1) Node A(Command Data) - to create the socket (including creating a socket, assigning IP & Port no and establishing connection) and to transmit the data(TCP Packets).

sockfd = socket(AF_INET, SOCK_STREAM, 0); 
if (sockfd == -1) 
{ 
    cout<<"\n socket creation failed...\n";
    exit(0); 
} 
else
{
    cout<<"\n Socket successfully created..\n";
}

bzero(&servaddr, sizeof(servaddr));
Sock_sts_flag = SET;

servaddr.sin_family = AF_INET; 
servaddr.sin_addr.s_addr = inet_addr(IP_ADDRESS);
servaddr.sin_port = htons(PORT_LCU);

if (connect(sockfd, (SA*)&servaddr, sizeof(servaddr)) != 0)
{
    cout<<"\n Connection with the server failed...\n";
    exit(0); 
} 
else
{
        cout<<"\n Connected to the server...\n";
}

2) Node B(Feedback) - to read the data from the same socket.

n = read(sockfd, buff_lcu, MAX_ARRAY_SIZE_FB);

cout<<"\n n = " <<n;

if(n < 0)
{
    cout<<"\n Couldn't Read from Socket";
}
else
{
      // Perform task
}

I am able to achieve the first part of the problem, which is creating a TCP/IP socket and establish the connection between the Client & Server and transmit data from the Client. I have even validated the received packets on the server side and its fine.

My Server is also sending the feedback data in the same socket once the connection is established but I am not able to read that data if I launch my Node B.

I verified the packets sent by my Server using

$ sudo tcpdump -XX -i enp1os

and I am receiving the expected packets.

When ever I launch my Node B it come and stops at the read() and doesn't proceed even though it is in a While loop.

I even tried sending the sockfd via a ROS service from Node A (Service - Client) to Node B (Service - Server) and receiving the actual value of the sockfd but still not able to read the data via Node B.

Kindly suggest a solution for this.

Thanks