Example socket
This is a guide to the socket C example project included in the EMAC OE SDK.
This application demonstrates how to set up sockets for host and client nodes on an ethernet network.
The socket project builds one executable: socket.
Contents
Opening, Building and Uploading the Project Files
stub
Usage and Behavior
Hardware Requirements
The socket C example project will run just fine on any system for which it can be compiled.
Using socket
./socket -sc [ADDRESS] PORT
- -s
- Create a server, specify the PORT to listen to.
- -c
- Create a client, specify the server's ADDRESS and PORT.
For our demonstration we create a server and a client. Upon activation the server waits for a connection. Upon activation the client connects with the server. When the server detects the client's connection it sends a message to the client. Then the client sends that message right back to the server. The server compares the message it sent to the client with the message it just got from the client. If they match then we have performed a successful transmission.
Usage Example. One machine
We're going to create a server and client on the same machine. The machine will talk to itself.
Create the server
Note We're using port 9999. It's arbitrarily chosen and assumed to be free.
root@som9g20:/tmp# ./socket -s 9999
Starting server
Making socket
Binding to port 9999opened socket as fd (3) on port (9999) for stream i/o
Server
sin_family = 2
sin_addr.s_addr = 0
sin_port = 9999
Making a listen queue of 5 elements
Waiting for a connection
...and it's waiting for a connection. Note that you can't do anything else in this console because it's occupied with the socket program. So open another console and, if necessary, log-on.
Create the client.
Note We're using port 9999, the same port for which the server is configured; and the localhost address: 127.0.0.1
root@som9g20:/tmp# ./socket -c 127.0.0.1 9999
Making a socket
Connecting to 127.0.0.1 on port 9999
Received "Message from the socket server" from server
Writing "Message from the socket server" to server
Closing socket
This is what happened: The server started up and waited for a connection. Then we started the client and it immediately connected to the server. The server noticed that connection and sent a message to the client: "Message from the socket server". The client received the message and sent it right back to the server. The server compared the two messages to check the accuracy of the transmission. The messages matched so the transmission was successful.
Usage Example. Two machines
Get 2 machines. They can be ARM machines, PCs or whatever. We're going to refer to our machines as MACHINE0 and MACHINE1.
Compile and upload the socket executable to each of them.
Connect them both to the same ethernet network.
On MACHINE0 run the socket program.
som9g45:/tmp# ./socket -s 9999
Note that we specified -s, thus configuring MACHINE0 as a server. 9999 is an arbitrarily chosen (and assumed to be free) port address on the host machine.
So now MACHINE0 has been configured as a server and it's waiting for a connection...
On MACHINE1 run the socket program.
som9g20:/tmp# ./socket -c 10.0.2.204 9999
Note that we specified -c, thus configuring MACHINE1 as a client. 10.0.2.204 is the host machine's address (this will need to be determined. Use minicom or something similar). 9999 is the port address on the host machine.
On MACHINE0 you will see something like this:
som9g45:/tmp# ./socket -s 9999
Starting server
Making socket
Binding to port 9999opened socket as fd (3) on port (9999) for stream i/o
Server
sin_family = 2
sin_addr.s_addr = 0
sin_port = 9999
Making a listen queue of 5 elements
Waiting for a connection
Got a connection
Sending "Message from the socket server" to client
The messages match
Closing the socket
Waiting for a connection
On MACHINE1 you will see something like this:
root@som9g20:/tmp# ./socket -c 10.0.2.204 9999
Making a socket
Connecting to 10.0.2.204 on port 9999
Received "Message from the socket server" from server
Writing "Message from the socket server" to server
Closing socket
This is what happened: MACHINE0 (the server) was configured as a server and waited for a connection. MACHINE1 (the client) connected to MACHINE0. MACHINE0 noticed the connection and sent a message to MACHINE1: "Message from the socket server". MACHINE1 received the message and sent it right back. MACHINE0 compared the two messages to check the accuracy of the transmission. The messages matched so the transmission was successful.
Summary
The socket C example project demonstrates how to set up host and client node sockets on an ethernet network.
