JarCastingSocksLib 
SocksLib is a Java library for SOCKS5 protocol.
See Wiki Page (Chinese)
If you are looking for a SOCKS5 server instead of a SOKCS5 library, I hope Esocks can help you.
References
Features
Client
- TCP proxy
- UDP proxy
- Bind
- Anonymous authentication
- USERNAME/PASSWORD authentication
- Proxy chain
Server
- TCP proxy
- UDP proxy
- Bind
- Anonymous authentication
- USERNAME/PASSWORD authentication
- Proxy chain
- Black or white IP lists for clients
Quick start
Environment
- JDK 8+
Dependencies
You should put following libraries in your project's CLASSPATH:
SOCKS5 Client
CONNECT
SocksProxy proxy = new Socks5(new InetSocketAddress("localhost",1080));
Socket socket = new SocksSocket(proxy, new InetSocketAddress("whois.internic.net",43));
Connect SOCKS5 server using SSL connection
SSLConfigurationBuilder builder = SSLConfigurationBuilder.newBuilder();
builder.setTrustKeyStorePath("client-trust-keystore.jks");
builder.setTrustKeyStorePassword("123456");
SocksProxy proxy = new SSLSocks5(new InetSocketAddress("localhost", 1081), builder.build());
Socket socket = new SocksSocket(proxy, new InetSocketAddress("whois.internic.net",43));
BIND
SocksServerSocket serverSocket = new SocksServerSocket(proxy, inetAddress,8080);
InetAddress bindAddress = serverSocket.getBindAddress();
int bindPort = serverSocket.getBindPort();
Socket socket = serverSocket.accept();
UDP ASSOCIATE
DatagramSocket socket = new Socks5DatagramSocket(proxy);
SOCKS5 Server
SocksProxyServer proxyServer = SocksServerBuilder.buildAnonymousSocks5Server();
proxyServer.start();// Creat a SOCKS5 server bind at port 1080
SSL socks server
SSLConfigurationBuilder builder = SSLConfigurationBuilder.newBuilder();
builder.setKeyStorePath("server-keystore.jks");
builder.setKeyStorePassword("123456");
builder.setClientAuth(false);
socksProxyServer = SocksServerBuilder.buildAnonymousSSLSocks5Server(1081, builder.build());
socksProxyServer.start();