Question

The connect method fails giving an EINVAL when I am trying to connect from blue.example.edu to green.example.edu

I do not get this error when I connect from blue to blue itself.

The Ruby documentation under connect suggests

Errno::EINVAL – the address length used for the sockaddr is not a
valid length for the address family or there is an invalid family in
sockaddr

But since the same parameter is working correctly when I try connecting blue to another port on itself, this might be wrong ?

Here is the code snippet:

MY_NAME = Socket.gethostname
SERVER_NAME = "blue"    # Socket.gethostname returns 'blue' on the server
SERVER_IP = Socket::getaddrinfo(SERVER_NAME, 'www', nil, Socket::SOCK_STREAM)[0][3]  
#--> Gives me A.B.C.27 (see note on ipconfig below)

SERVER_LISTENING_PORT = 34900

MY_NAME = Socket.gethostname
MY_PORT_FOR_REQUESTING_SERVER = 40000

# other stuff

#CREATE
client_socket = Socket::new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
client_socket_addr = Socket.pack_sockaddr_in(MY_PORT_FOR_REQUESTING_SERVER, MY_NAME)

#BIND
client_socket.bind(client_socket_addr)

#CONNECT
server_addr = Socket.pack_sockaddr_in(SERVER_LISTENING_PORT, SERVER_NAME)
i_tried_with_ip_address_also = Socket.pack_sockaddr_in(SERVER_LISTENING_PORT, SERVER_IP)

#The line below raises the error
client_socket.connect(server_addr)

# more code below

Please note that hitting ifconfig on blue yields the same A.B.C.27 what the SERVER_IP contains

Under eth1 - inet addr:A.B.C.27, Bcast:A.B.C.255 Mask:255.255.255.0

I’m guessing this is related to the issue ?

Using Ruby 1.8.7 on Ubuntu machines

Please advice.

---

EDIT:

I used TCPSocket as suggested by zed_0xff in order to get this working temporarily.
However I wish to know why the regular socket way is not working.

The only difference I can see is that using the Socket class, I am binding the client_socket_addr to a port from which I wish to send my data.
TCPSocket sends data from a random port to the specified listening port on the server.
What do I do if I wish to bind the sending to a specific port ?

---

EDIT2: Changed question title from:

Ruby Sockets: Errno::EINVAL: Invalid argument – connect(2)

So the answer from @zed_0xff has helped me tackle one of my problems of actually establishing a connection between the client and the server (Thank you!)

However, with that method, TCPSocket chooses a random sending port for sending data. Trying to binding the sending port to a particular port number fails.

---

PS: Please let me know if modifying the question name is against the community guidelines. Since my issue was only partially resolved, I edited the title it here itself and explained the edits in the “Edit” sections.

Answer 1

Getting EINVAL for bind() indicates that the address to bind to might still be in use.

To get around this

• either use a different address (ip-address and/or port)
• or if you are wanting to reuse a address, set the socket option SO_REUSEADDR on the socket prior to using it
• or do not bind … 😉