Detailed explanation of python series-socket library application
Article directory
1. Functions of the socket library
| Function name | parameter | effect |
|---|---|---|
| gethostname() | no parameters | Return hostname |
| gethostbyname('hostname') | CPU name | Convert hostname to ipv4 address |
| gethostbyname_ex('hostname') | CPU name | Return host name, host alias list, host IP address list |
| gethostbyaddr('ip address') | IP address | Returns a triplet (hostname, list of host aliases, list of host IP addresses) |
| getservbyport(port number','protocol name') | Port number, protocol name | Returns the service name of this port number, limited to this machine |
| getservbyname('service name','protocol name') | Service name, protocol name | Returns the port number where the service is located |
| getsockname() | no parameters | Returns its own bundled IPv4 address |
| getaddrinfo('hostname','port number') | host name, port number | Returns a five-tuple, used to obtain the address information of the host name, compatible with ipv4 and ipv6 |
| socket(family,type) | family:socket.AF_INET(IPv4) socket.AF_INET6(IPv6) AF_UNIX (inter-process communication on the same machine) type:socket.SOCK_STREAM (TCP connection) socket.SOCK_DGRAM (UDP protocol) |
Create a connection with a known IP address and protocol type |
| connect((host,port)) | (host name, port number) | Connect remotely to the host's port, pay attention to the brackets |
| gettimeout() | no parameters | Returns the socket timeout time, unit is s |
| settimeout(timeout) | overtime time | Set socket timeout |
2. Methods of socket library
1.connect（address）:
Connect to a remote socket corresponding to address (IP address). If the connection is interrupted, this method will wait until the connection is completed, or throw a socket.timeout error
2.accept():
Accept a connection, but the premise is that the socket must have been bound to an address and is waiting for a connection. By default, sockets are blocking, which means that socket method calls will not return until the task is completed.
When the accept method is called, the socket will enter the "waiting" state. When the client requests a connection, the method establishes the connection and returns to the server. The accept method returns a tuple with two elements (connection, address). The first element, connection, is the new socket object through which the server must communicate with the client; the second element, address, is the client's Internet address.
3.recv(bufsize)：
Receive data from the socket, note that it is of byte type, and bufsize specifies the maximum data size received at one time.
4.recvfrom(bufsize) ：
The difference from the previous recv(bufsize) method is that in addition to the data, the return value also has the address to send the data. The return value is a data, address pair (data, address).
5.send(bytes):
To send data to the socket, the premise is that you have connected to the remote socket. The return value is the amount of data sent. It is the application's responsibility to check whether the data has been sent.
6.sendto(bytes, flags, address)：
Basically the same as socket.send().
7.close():
Close the connection. When socket.close() is executed, the underlying operations related to this connection will also be closed (such as the file descriptor). Once closed, operations on related file objects will fail.
8.bind(address)：
Bind the socket object to an address, but this address must not be occupied, otherwise the connection will fail.
The address here is generally an ip, port pair.
9.listen([backlog]) ：
Monitoring enables the server to receive server connections. If the backlog is specified (at least 0, if it is smaller than 0, the system defaults to 0), it limits the number of connections that can be made. If not specified, a default reasonable value will be assigned.