### VMess Server Setup and Handler Implementation in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

Provides a Go implementation for setting up a VMess server. It includes a basic 'ProxyHandler' to manage incoming TCP and UDP connections, forwarding them to their destinations. The server is configured with user credentials and listens on a specified port. Dependencies include 'sing-vmess', 'sing/common/metadata', and 'sing/common/network'.

```go
package main

import (
    "context"
    "net"
    "github.com/sagernet/sing-vmess"
    M "github.com/sagernet/sing/common/metadata"
    N "github.com/sagernet/sing/common/network"
)

// Handler implementation for proxying connections
type ProxyHandler struct{}

func (h *ProxyHandler) NewConnectionEx(ctx context.Context, conn net.Conn, source M.Socksaddr, destination M.Socksaddr, onClose N.CloseHandlerFunc) {
    // Handle TCP connection - dial to destination
    remote, err := net.Dial("tcp", destination.String())
    if err != nil {
        conn.Close()
        return
    }
    defer remote.Close()
    defer conn.Close()

    // Bidirectional copy
    go func() {
        buf := make([]byte, 32768)
        _, _ = copyBuffer(remote, conn, buf)
    }()
    buf := make([]byte, 32768)
    _, _ = copyBuffer(conn, remote, buf)
}

func (h *ProxyHandler) NewPacketConnectionEx(ctx context.Context, conn N.PacketConn, source M.Socksaddr, destination M.Socksaddr, onClose N.CloseHandlerFunc) {
    // Handle UDP packets
    defer conn.Close()

    remote, err := net.ListenPacket("udp", "")
    if err != nil {
        return
    }
    defer remote.Close()

    // Forward packets bidirectionally
    buffer := make([]byte, 65535)
    for {
        n, _, err := conn.ReadFrom(buffer)
        if err != nil {
            break
        }
        _, _ = remote.WriteTo(buffer[:n], destination.UDPAddr())
    }
}

func main() {
    handler := &ProxyHandler{}

    // Create service with handler
    service := vmess.NewService[string](handler)

    // Add users with their credentials
    users := []string{"user1", "user2"}
    userIds := []string{
        "b831381d-6324-4d53-ad4f-8cda48b30811",
        "a2c3e4f5-1234-5678-9abc-def012345678",
    }
    alterIds := []int{0, 0} // 0 for AEAD mode

    err := service.UpdateUsers(users, userIds, alterIds)
    if err != nil {
        panic(err)
    }

    err = service.Start()
    if err != nil {
        panic(err)
    }
    defer service.Close()

    // Listen for incoming connections
    listener, err := net.Listen("tcp", ":8388")
    if err != nil {
        panic(err)
    }
    defer listener.Close()

    println("VMess server listening on :8388")

    for {
        conn, err := listener.Accept()
        if err != nil {
            continue
        }

        go func(c net.Conn) {
            ctx := context.Background()
            source := M.SocksaddrFromNet(c.RemoteAddr())
            err := service.NewConnection(ctx, c, source, nil)
            if err != nil {
                c.Close()
            }
        }(conn)
    }
}

func copyBuffer(dst net.Conn, src net.Conn, buf []byte) (int64, error) {
    var written int64
    for {
        nr, err := src.Read(buf)
        if nr > 0 {
            nw, ew := dst.Write(buf[0:nr])
            if nw > 0 {
                written += int64(nw)
            }
            if ew != nil {
                return written, ew
            }
        }
        if err != nil {
            return written, err
        }
    }
}
```

--------------------------------

### Creating UDP Packet Connections in VMess Client Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

This example illustrates setting up a UDP packet connection through VMess for datagram proxying, useful for DNS or other UDP traffic. Dependencies include sing-vmess and metadata parsing; inputs are upstream TCP and UDP destination, outputs a packet connection for WriteTo/ReadFrom. Limitations encompass encapsulating UDP in TCP and potential performance overhead for high-volume datagrams.

```go
package main

import (
    "net"
    "github.com/sagernet/sing-vmess"
    M "github.com/sagernet/sing/common/metadata"
)

func main() {
    client, err := vmess.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",
        "aes-128-gcm",
        0,
    )
    if err != nil {
        panic(err)
    }

    upstream, err := net.Dial("tcp", "proxy.example.com:443")
    if err != nil {
        panic(err)
    }

    destination := M.ParseSocksaddr("8.8.8.8:53")

    // Create UDP packet connection
    packetConn, err := client.DialPacketConn(upstream, destination)
    if err != nil {
        upstream.Close()
        panic(err)
    }
    defer packetConn.Close()

    // Send DNS query
    dnsQuery := []byte{
        0x00, 0x01, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x06, 0x67, 0x6f, 0x6f,
        0x67, 0x6c, 0x65, 0x03, 0x63, 0x6f, 0x6d, 0x00,
        0x00, 0x01, 0x00, 0x01,
    }

    _, err = packetConn.WriteTo(dnsQuery, destination.UDPAddr())
    if err != nil {
        panic(err)
    }

    response := make([]byte, 512)
    n, addr, err := packetConn.ReadFrom(response)
    if err != nil {
        panic(err)
    }
    println("Received", n, "bytes from", addr.String())
}
```

--------------------------------

### Use VLESS for UDP and XUDP Traffic in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

This Go code demonstrates how to utilize VLESS for UDP traffic, supporting both standard UDP and the enhanced XUDP protocol. It requires the sing-vmess library. The examples show creating a VLESS client and then using DialPacketConn for standard UDP and DialXUDPPacketConn for XUDP, allowing for specific packet routing and reading with source address information.

```go
package main

import (
    "net"
    "github.com/sagernet/sing-vmess/vless"
    "github.com/sagernet/sing-vmess"
    M "github.com/sagernet/sing/common/metadata"
    "github.com/sagernet/sing/common/logger"
    "github.com/sagernet/sing/common/buf"
)

func main() {
    client, err := vless.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",
        "",  // No flow for UDP
        logger.NOP(),
        "",
    )
    if err != nil {
        panic(err)
    }

    // Example 1: Standard UDP packet connection
    upstream1, _ := net.Dial("tcp", "vless.example.com:443")
    destination := M.ParseSocksaddr("8.8.8.8:53")

    packetConn, err := client.DialPacketConn(upstream1, destination)
    if err != nil {
        upstream1.Close()
        panic(err)
    }
    defer packetConn.Close()

    // Send UDP data
    _, err = packetConn.Write([]byte("DNS query data"))
    if err != nil {
        panic(err)
    }

    // Example 2: XUDP for enhanced UDP with addressing
    upstream2, _ := net.Dial("tcp", "vless.example.com:443")

    xudpConn, err := client.DialXUDPPacketConn(upstream2, M.ParseSocksaddr("0.0.0.0:0"))
    if err != nil {
        upstream2.Close()
        panic(err)
    }
    defer xudpConn.Close()

    // Write packet to specific destination
    buffer := buf.NewSize(512)
    buffer.Write([]byte("XUDP packet data"))
    target := M.ParseSocksaddr("192.168.1.1:53")

    err = xudpConn.WritePacket(buffer, target)
    if err != nil {
        panic(err)
    }

    // Read with source address information
    recvBuf := buf.NewSize(2048)
    srcAddr, err := xudpConn.ReadPacket(recvBuf)
    if err != nil {
        panic(err)
    }
    defer recvBuf.Release()

    println("Received from", srcAddr.String())
}
```

--------------------------------

### Create VLESS Client for Basic Proxy Connections in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

This Go code demonstrates how to create a VLESS client to establish basic proxy connections. It supports optional XTLS vision flow control. Dependencies include the sing-vmess library. The function takes a user UUID, flow control type, logger, and encryption options as input, and returns a VLESS client for establishing connections.

```go
package main

import (
    "net"
    "github.com/sagernet/sing-vmess/vless"
    M "github.com/sagernet/sing/common/metadata"
    "github.com/sagernet/sing/common/logger"
)

func main() {
    // Create VLESS client
    client, err := vless.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",  // User UUID
        "xtls-rprx-vision",                       // Flow: "" or "xtls-rprx-vision"
        logger.NOP(),                             // Logger
        "",                                       // Encryption options (empty for none)
    )
    if err != nil {
        panic(err)
    }

    // Connect to VLESS server (typically over TLS)
    upstream, err := net.Dial("tcp", "vless.example.com:443")
    if err != nil {
        panic(err)
    }

    destination := M.ParseSocksaddr("www.example.com:443")

    // Dial connection through VLESS
    conn, err := client.DialConn(upstream, destination)
    if err != nil {
        upstream.Close()
        panic(err)
    }
    defer conn.Close()

    // Use connection for HTTPS traffic
    _, err = conn.Write([]byte("GET / HTTP/1.1\r\nHost: www.example.com\r\n\r\n"))
    if err != nil {
        panic(err)
    }

    response := make([]byte, 4096)
    n, err := conn.Read(response)
    if err != nil {
        panic(err)
    }
    println("Received:", string(response[:n]))
}
```

--------------------------------

### Creating and Dialing VMess Client Connections in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

This snippet demonstrates initializing a VMess client with UUID, security type, and AlterID, then dialing a TCP connection to a destination via the proxy server. It depends on the sing-vmess and sing/common/metadata packages; inputs include server address and destination sockaddr, outputs a proxied connection for reading/writing. Limitations include requiring a valid upstream connection and handling errors for failed handshakes.

```go
package main

import (
    "net"
    "github.com/sagernet/sing-vmess"
    M "github.com/sagernet/sing/common/metadata"
)

func main() {
    // Create VMess client with user UUID and security type
    client, err := vmess.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",  // User UUID
        "aes-128-gcm",                            // Security: "none", "aes-128-cfb", "aes-128-gcm", "chacha20-poly1305", "auto"
        0,                                        // AlterID (0 for AEAD, >0 for legacy)
    )
    if err != nil {
        panic(err)
    }

    // Establish TCP connection to VMess server
    upstream, err := net.Dial("tcp", "proxy.example.com:443")
    if err != nil {
        panic(err)
    }

    // Dial through VMess to final destination
    destination := M.ParseSocksaddr("www.google.com:443")
    conn, err := client.DialConn(upstream, destination)
    if err != nil {
        upstream.Close()
        panic(err)
    }
    defer conn.Close()

    // Use connection for encrypted communication
    _, err = conn.Write([]byte("GET / HTTP/1.1\r\nHost: www.google.com\r\n\r\n"))
    if err != nil {
        panic(err)
    }

    buffer := make([]byte, 4096)
    n, err := conn.Read(buffer)
    if err != nil {
        panic(err)
    }
    println(string(buffer[:n]))
}
```

--------------------------------

### Establishing Early VMess Connections for Zero RTT in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

This code shows creating an early VMess connection that postpones the handshake until the first write operation, enabling zero RTT latency. It relies on the same dependencies as standard client creation; inputs are client config and destination, outputs a deferred-handshake connection. Limitations involve potential handshake failures on first write and suitability for scenarios needing immediate data send.

```go
package main

import (
    "net"
    "github.com/sagernet/sing-vmess"
    M "github.com/sagernet/sing/common/metadata"
)

func main() {
    client, err := vmess.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",
        "chacha20-poly1305",
        0,
    )
    if err != nil {
        panic(err)
    }

    upstream, err := net.Dial("tcp", "proxy.example.com:443")
    if err != nil {
        panic(err)
    }

    destination := M.ParseSocksaddr("api.example.com:443")

    // Early connection doesn't send handshake immediately
    conn := client.DialEarlyConn(upstream, destination)
    defer conn.Close()

    // Handshake is sent with first write (zero RTT)
    payload := []byte("GET /api/data HTTP/1.1\r\nHost: api.example.com\r\n\r\n")
    _, err = conn.Write(payload)
    if err != nil {
        panic(err)
    }

    response := make([]byte, 8192)
    n, err := conn.Read(response)
    if err != nil {
        panic(err)
    }
    println("Response:", string(response[:n]))
}
```

--------------------------------

### VMess Client XUDP Connection in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

Demonstrates setting up a VMess client that uses the XUDP protocol for connecting to a proxy. It establishes a connection, sends a UDP packet with a specific destination, and receives a response, preserving source address information. Requires the 'sing-vmess' and 'sing' libraries.

```go
package main

import (
    "net"
    "github.com/sagernet/sing-vmess"
    M "github.com/sagernet/sing/common/metadata"
    "github.com/sagernet/sing/common/buf"
)

func main() {
    client, err := vmess.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",
        "aes-128-gcm",
        0,
    )
    if err != nil {
        panic(err)
    }

    upstream, err := net.Dial("tcp", "proxy.example.com:443")
    if err != nil {
        panic(err)
    }

    destination := M.ParseSocksaddr("example.com:0")

    // Create XUDP connection with mux support
    xudpConn, err := client.DialXUDPPacketConn(upstream, destination)
    if err != nil {
        upstream.Close()
        panic(err)
    }
    defer xudpConn.Close()

    // Write packet with specific destination
    buffer := buf.NewSize(256)
    buffer.Write([]byte("Hello XUDP"))

    targetAddr := M.ParseSocksaddr("192.168.1.100:8080")
    err = xudpConn.WritePacket(buffer, targetAddr)
    if err != nil {
        panic(err)
    }

    // Read packet with source address
    recvBuffer := buf.NewSize(2048)
    srcAddr, err := xudpConn.ReadPacket(recvBuffer)
    if err != nil {
        panic(err)
    }
    println("Received from", srcAddr.String(), ": ", string(recvBuffer.Bytes()))
    recvBuffer.Release()
}
```

--------------------------------

### Configure VMess Client with Advanced Options in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

This Go code illustrates how to configure a VMess client with advanced options using the sing-vmess library. It allows for enabling global padding, authenticated length encryption, and custom time functions. These options enhance traffic obfuscation and security. The function signature for NewClient includes parameters for UUID, cipher, port, and variadic client options.

```go
package main

import (
    "time"
    "github.com/sagernet/sing-vmess"
)

func main() {
    // Create client with advanced options
    client, err := vmess.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",
        "aes-128-gcm",
        0,
        vmess.ClientWithGlobalPadding(),              // Enable global padding
        vmess.ClientWithAuthenticatedLength(),        // Enable authenticated length
        vmess.ClientWithTimeFunc(time.Now),           // Custom time function
    )
    if err != nil {
        panic(err)
    }

    // GlobalPadding adds random padding to all chunks for traffic obfuscation
    // AuthenticatedLength encrypts chunk length information
    // TimeFunc allows custom time source (useful for testing or time sync)

    _ = client // Use client for connections as shown in previous examples
}
```

--------------------------------

### Implement Mux-aware VMess Server in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

This snippet creates a VMess server with multiplexing support using the sing-vmess library. It includes a MuxHandler for TCP and UDP stream forwarding, user configuration, and a listener on port 8388. Requires the sing-vmess and related sing packages.

```go
package main

import (
    "context"
    "net"
    "github.com/sagernet/sing-vmess"
    M "github.com/sagernet/sing/common/metadata"
    N "github.com/sagernet/sing/common/network"
)

// Mux-aware handler
type MuxHandler struct{}

func (h *MuxHandler) NewConnectionEx(ctx context.Context, conn net.Conn, source M.Socksaddr, destination M.Socksaddr, onClose N.CloseHandlerFunc) {
    // Handle individual TCP stream within mux
    remote, err := net.Dial("tcp", destination.String())
    if err != nil {
        conn.Close()
        return
    }

    // Bidirectional forwarding
    go copyData(conn, remote)
    copyData(remote, conn)

    remote.Close()
    conn.Close()
}

func (h *MuxHandler) NewPacketConnectionEx(ctx context.Context, conn N.PacketConn, source M.Socksaddr, destination M.Socksaddr, onClose N.CloseHandlerFunc) {
    // Handle UDP stream within mux
    defer conn.Close()

    remote, err := net.ListenPacket("udp", "")
    if err != nil {
        return
    }
    defer remote.Close()

    buffer := make([]byte, 65535)
    for {
        n, _, err := conn.ReadFrom(buffer)
        if err != nil {
            break
        }
        _, _ = remote.WriteTo(buffer[:n], destination.UDPAddr())
    }
}

func copyData(dst net.Conn, src net.Conn) {
    buffer := make([]byte, 32768)
    for {
        n, err := src.Read(buffer)
        if err != nil {
            break
        }
        _, err = dst.Write(buffer[:n])
        if err != nil {
            break
        }
    }
}

func main() {
    handler := &MuxHandler{}
    service := vmess.NewService[string](handler)

    // Configure service with users
    _ = service.UpdateUsers(
        []string{"user1"},
        []string{"b831381d-6324-4d53-ad4f-8cda48b30811"},
        []int{0},
    )
    _ = service.Start()
    defer service.Close()

    // Accept connections and handle mux
    listener, _ := net.Listen("tcp", ":8388")
    defer listener.Close()

    println("Mux-enabled VMess server on :8388")

    for {
        conn, err := listener.Accept()
        if err != nil {
            continue
        }

        go func(c net.Conn) {
            ctx := context.Background()
            source := M.SocksaddrFromNet(c.RemoteAddr())
            // HandleMuxConnection is called automatically by service
            _ = service.NewConnection(ctx, c, source, nil)
        }(conn)
    }
}
```

--------------------------------

### Define VMess Protocol Constants in Go

Source: https://context7.com/xchacha20-poly1305/sing-vmess/llms.txt

Declares security types, command types, and request options as constants for VMess protocol configuration. Includes constants for AES-128-CFB, AES-128-GCM, ChaCha20-Poly1305, and None security modes. Defines TCP, UDP, and Mux command types. Specifies request options as bitflags for chunk streaming, connection reuse, chunk masking, global padding, and authenticated length.

```go
package main

import (
    "github.com/sagernet/sing-vmess"
)

func main() {
    // Security Types
    const (
        SecurityTypeLegacy           = 1  // AES-128-CFB (legacy)
        SecurityTypeAuto             = 2  // Auto-select based on platform
        SecurityTypeAes128Gcm        = 3  // AES-128-GCM (recommended)
        SecurityTypeChacha20Poly1305 = 4  // ChaCha20-Poly1305
        SecurityTypeNone             = 5  // No encryption (not recommended)
    )

    // Command Types
    const (
        CommandTCP = 1  // TCP connection
        CommandUDP = 2  // UDP connection
        CommandMux = 3  // Multiplexed connection
    )

    // Request Options (bitflags)
    const (
        RequestOptionChunkStream         = 1  // Use chunk streaming
        RequestOptionConnectionReuse     = 2  // Enable connection reuse
        RequestOptionChunkMasking        = 4  // Mask chunk boundaries
        RequestOptionGlobalPadding       = 8  // Add global padding
        RequestOptionAuthenticatedLength = 16 // Authenticate chunk lengths
    )

    // Example: Creating client with auto security
    client, err := vmess.NewClient(
        "b831381d-6324-4d53-ad4f-8cda48b30811",
        "auto",  // Will use AES-128-GCM on amd64/arm64, ChaCha20-Poly1305 otherwise
        0,
    )
    if err != nil {
        panic(err)
    }

    _ = client
}
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.