fields in /proc/net/tcp* are not always delimited by single space

Using split(' '):
```
>>> f = open('/proc/net/tcp')
>>> f.readline().strip().split(' ')
['sl', '', 'local_address', 'rem_address', '', '', 'st', 'tx_queue', 'rx_queue', 'tr', 'tm->when', 'retrnsmt', '', '', 'uid', '', 'timeout', 'inode']
```
Index of 'local_address' in the outputted list = 2

Using split():
```
>>> f = open('/proc/net/tcp')
>>> f.readline().strip().split()
['sl', 'local_address', 'rem_address', 'st', 'tx_queue', 'rx_queue', 'tr', 'tm->when', 'retrnsmt', 'uid', 'timeout', 'inode']
```
Index of 'local_address' in the outputted list = 1 (which is what the code expects: `local_address_field = 1`)