# Networking

## Sockets

Basic network communication over raw sockets

```python
# Basic TCP connection to a server to send and receive data
import socket

clientsocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
clientsocket.connect(('127.0.0.1', 9987))
clientsocket.send('hello'.encode())
data = clientsocket.recv(1024)
print(data)
```

## SSH Interaction

Paramiko is a useful library which can be used to log into a host over SSH and execute commands as though it were an interactive session.

```python
import paramiko

key = '/home/some/rsa/private/key'
hostname = '127.0.0.1'
user = 'm4lwhere'

k = paramiko.RSAKey.from_private_key_file(key)
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(hostname=hostname, username=user, pkey=k)
stdin, stdout, stderr = client.exec_command('ls -l')
print(f'Received output:\n\n{stdout}')

# Don't forget to close out the object!
ssh.close()
```

### SFTP

Paramiko can additionally support SFTP natively with a `paramiko.SSHClient()` object which is super cool.

```python
import paramiko

key = '/home/some/rsa/private/key'
hostname = '127.0.0.1'
user = 'm4lwhere'

k = paramiko.RSAKey.from_private_key_file(key)
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(hostname=hostname, username=user, pkey=k)

sftp = ssh.open_sftp()
srcFiles = sftp.listdir('/home/m4lwhere')

# Download each of the files in the srcFiles list
for i in srcFiles:
    download = f'/home/m4lwhere/{i}'
    sftp.get(download, '/opt/downloads')

# Upload a file from local machine to external one
sftp.put('/opt/upload.txt', '/home/m4lwhere/upload.txt')

ssh.close()
```


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