Example: Use Socket Api in WAMR

The related code/working directory of this example resides in directory {WAMR_DIR}/samples/socket-api

This sample demonstrates how to use WAMR socket-api to develop wasm network applications. Two wasm applications are provided: tcp-server and tcp-client, and this sample demonstrates how they communicate with each other.

Preparation

Please install WASI SDK, download the wasi-sdk release and extract the archive to default path /opt/wasi-sdk. And install wabt, download the wabt release and extract the archive to default path /opt/wabt

Build the sample

mkdir build
cd build
cmake ..
make

iwasm and the following Wasm modules (along with their corresponding native version) will be generated:

• addr_resolve.wasm, addr_resolve

• send_recv.wasm, send_recv

• socket_opts.wasm, socket_opts

• tcp_client.wasm, tcp_client

• tcp_server.wasm, tcp_server

• udp_client.wasm, udp_client

• udp_server.wasm, udp_server

Note that iwasm is built with libc-wasi and lib-pthread enabled.

Run workload

TCP client/server

Start the tcp server, which opens port 1234 and waits for clients to connect.

cd build
./iwasm --addr-pool=0.0.0.0/15 tcp_server.wasm

Start the tcp client, which connects the server and receives message.

cd build
./iwasm --addr-pool=127.0.0.1/15 tcp_client.wasm

The output of client is like:

[Client] Create socket
[Client] Connect socket
[Client] Client receive
[Client] 115 bytes received:
Buffer received:
Say Hi from the Server
Say Hi from the Server
Say Hi from the Server
Say Hi from the Server
Say Hi from the Server

[Client] BYE

send_recv.wasm contains a thread as a server and a thread as a client. They send and receive data via 127.0.0.1:1234.

$ ./iwasm --addr-pool=127.0.0.1/0 ./send_recv.wasm

The output is:

Server is online ...
Client is running...
Start receiving.
Start sending.
Send 106 bytes successfully!
Receive 106 bytes successfully!
Data:
  The stars shine down
  It brings us light
  Light comes down
  To make us paths
  It watches us
  And mourns for us

Socket options

socket_opts.wasm shows an example of getting and setting various supported socket options

$ ./iwasm socket_opts.wasm

The output is:

[Client] Create TCP socket
[Client] Create UDP socket
[Client] Create UDP IPv6 socket
setsockopt SO_RCVTIMEO result is expected
getsockopt SO_RCVTIMEO result is expected
...
[Client] Close sockets

The timeout_client.wasm and timeout_server.wasm examples demonstrate socket send and receive timeouts using the socket options. Start the server, then start the client.

$ ./iwasm --addr-pool=0.0.0.0/15 timeout_server.wasm

The output is:

Wait for client to connect
Client connected, sleeping for 10s
Shutting down

$ ./iwasm --addr-pool=127.0.0.1/15 timeout_client.wasm

The output is:

Waiting on recv, which should timeout
Waiting on send, which should timeout
Success. Closing socket 

The multicast_client and multicast_server examples demonstrate receiving multicast packets in WASM. Start the client and then the server with a multicast IP address and port.

$ ./iwasm --addr-pool=0.0.0.0/0,::/0 multicast_client.wasm <Multicast IP> <Port>
$ ./iwasm --addr-pool=0.0.0.0/0,::/0 multicast_client.wasm 224.0.0.1
$ ./iwasm --addr-pool=0.0.0.0/0,::/0 multicast_client.wasm FF02:113D:6FDD:2C17:A643:FFE2:1BD1:3CD2

The output should be

Joined multicast group. Waiting for datagram...
Reading datagram message...OK.
The message from multicast server is: "Test message"

$ ./multicast_server <Multicast IP> <Port>
$ ./multicast_server 224.0.0.1
$ ./multicast_server FF02:113D:6FDD:2C17:A643:FFE2:1BD1:3CD2

The output should be

Datagram sent

Domain name server resolution

addr_resolve.wasm demonstrates the usage of resolving a domain name

$ ./iwasm --allow-resolve=*.com addr_resolve.wasm github.com

The command displays the host name and its corresponding IP address:

Host: github.com
IPv4 address: 140.82.121.4 (TCP)

UDP client/server

Start the UDP server, which opens port 1234 and waits for clients to send a message.

cd build
./iwasm --addr-pool=0.0.0.0/15 udp_server.wasm

Start the tcp client, which sends a message to the server and waits for the response.

cd build
./iwasm --addr-pool=127.0.0.1/15 udp_client.wasm

The output of client is like:

[Client] Create socket
[Client] Client send
[Client] Client receive
[Client] Buffer received: Hello from server
[Client] BYE

The output of the server is like:

[Server] Create socket
[Server] Bind socket
[Server] Wait for clients to connect ..
[Server] received 17 bytes from 127.0.0.1:60927: Hello from client

Documentation

Refer to socket api document for more details.