Network

This document introduces a set of functions about TCP and UDP in Melang.

Import

net = Import('net');

tcp_connect

create a TCP connection to server.

net.tcp_connect(host, service, timeout);

Input:

• host - a string value. It can be an IP or domain name.
• service - a string value. It can be a port number or protocol name, like: http, 80.
• timeout - a millisecond timer. It’s an optional argument. It must be an positive integer or zero (timeout immediately). Omit means never timeout.

Return value:

• a TCP socket file descriptor return on success
• nil on timed out
• otherwise false returned

tcp_listen

Set up a TCP listen socket.

net.tcp_listen(host, service);

Input:

• host - a string value. It can be an IP or domain name.
• service - a string value. It can be a port number or protocol name, like: http, 80.

Return value:

• a TCP socket file descriptor return on success, otherwise false returned.

tcp_accept

Accept a TCP connection.

net.tcp_accept(listenfd, timeout);

Input:

• listened - an integer value generated by tcp_listen.
• timeout - a millisecond timer. It’s an optional argument. It should be an positive integer or zero (timeout immediately). Omit means never timeout.

Return value:

• a TCP socket file descriptor return on success.
• If timeout >= 0 and no TCP arrived, nil will be returned.
• Otherwise, false returned.

tcp_send

Send data via TCP.

net.tcp_send(sockfd, data);

Input:

• socked - a socket file descriptor which is an integer.
• data - a string value.

Return value:

• true on success, otherwise false returned.

tcp_recv

Receive data from TCP.

net.tcp_recv(sockfd, timeout);

Input:

• sockfd - a socket file descriptor which is an integer.
• timeout - a millisecond timer. It’s an optional argument. It must be an positive integer or zero (timeout immediately). Omit means never timeout.

Return value:

• Received data will be returned on success.
• If timeout >= 0 and no data arrived, nil will be returned.
• If TCP closed, true will be returned.
• Otherwise false returned.

tcp_close

Close a TCP connection.

net.tcp_close(sockfd);

Input:

• sockfd - a socket file descriptor which is an integer.

Return value:

• Always nil.

tcp_shutdown

Shutdown TCP connection.

net.tcp_shutdown(sockfd, mode);

Input:

• sockfd - a socket file descriptor which is an integer.
• mode - a string and only has two values: send and recv.

Return value:

• Always nil.

net.udp_create

Create an UDP socket.

net.udp_create(host, service);

Input:

• host - a string value. It can be an IP or domain name.
• service - a string value. It can be a port number or protocol name, like: http, 80.

Return value:

• a TCP socket file descriptor return on success, otherwise false returned.

udp_close

Close an UDP socket.

net.udp_close(fd);

Input:

• fd - an UDP socket file descriptor generated by udp_create.

Return value:

• Always nil.

udp_send

Send data via UDP.

net.udp_send(fd, data, host, service);

Input:

• fd. - an UDP socket file descriptor generated by udp_create.
• data - a string value.
• host - a string value. It can be an IP or domain name. This is the destination host.
• service - a string value. It can be a port number or protocol name, like: http, 80. This is the destination service name.

Return value:

• true will be returned on success, otherwise false returned.

udp_recv

Receive data from UDP.

net.udp_recv(fd, bufsize, &ip, &port, timeout);

Input:

• fd - an UDP socket file descriptor generated by udp_create.
• bufsize - an integer indicates the UDP receiving buffer size.
• ip - sender’s IP. This is an output argument.
• port - sender’s port. This is an output argument.
• timeout - a millisecond timer. It’s an optional argument. It should be an positive integer or zero (timeout immediately). Omit means never timeout.

Return value:

• Received data will be returned on success.
• If timeout >= 0 and no data arrived, nil will be returned.
• Otherwise false returned.

Example

//client.mln
net = Import('net');
sys = Import('sys');

fd = net.tcp_connect('127.0.0.1', '1234');
sys.print(fd);
net.tcp_send(fd, 'Hello');
sys.print(net.tcp_recv(fd));
net.tcp_close(fd);

//server.mln
net = Import('net');
sys = Import('sys');

listenfd = net.tcp_listen('127.0.0.1', '1234');
connfd = net.tcp_accept(listenfd);
sys.print(net.tcp_recv(connfd));
net.tcp_send(connfd, 'Hi');
net.tcp_close(connfd);

$ melang server.mln client.mln

The output is:

10
Hello
Hi