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Cheat Sheet Series
Network Programming with Go
Operators Comments Functions TCP Socket programming
Attribution:
Arithmetic operators // Line comments
func function_name( [parameter list] ) [return_types]
https://www.linode.com/docs/development/go/developing-udp-and-tcp-clients-and-servers-in-go/#create-the-tcp
+ sum integers, floats, complex values, strings { -client
/* General comments - closed */
Structure
Function body
- difference integers, floats, complex values
Create the TCP Client
}
* product integers, floats, complex values
Reserved Keywords //create a file named tcpC.go
/ quotient integers, floats, complex values
break • default • func • interface • select • case • defer • go • map • struct • chan •
AWS Lambda Function Handler in Go
package main
% remainder integers
else • goto • package • switch • const • fallthrough • if • range • type • continue • Based on AWS docs: https://docs.aws.amazon.com/lambda/latest/dg/golang-handler.html
& bitwise AND integers
for • import • return • var package main import (
| bitwise OR integers
"bufio"
^ bitwise XOR integers
import ( "fmt"
Controls
&^ bit clear (AND NOT) integers "fmt" "net"
if x > 0 {
"github.com/aws/aws-lambda-go/lambda" "os"
<< left shift integer << unsigned integer
return x
) "strings"
>> right shift integer >> unsigned integer
If, Else } else {
)
Comparison operators
return -x
type MyEvent struct {
== equal }
Name string 'json:"What is your name?"' func main() {
Age int 'json:"How old are you?"' arguments := os.Args
!= not equal
// Only `for`, no `while`, no `until`
} if len(arguments) == 1 {
< less
for i := 1; i < 10; i++ {
fmt.Println("Please provide host:port.")
<= less or equal
}
type MyResponse struct { return
> greater
for ; i < 10; { // while - loop
Message string 'json:"Answer:"' }
Loop }
>= greater or equal
}
for i < 10 { // omit semicolons if there is only a condition
CONNECT := arguments[1]
Logical operators
}
func HandleLambdaEvent(event MyEvent) (MyResponse, error) { c, err := net.Dial("tcp", CONNECT)
&& conditional AND p && q is "if p then q else false"
for { // you can omit the condition ~ while (true)
return MyResponse{Message: fmt.Sprintf("%s is %d years old!", event.Name,\ if err != nil {
|| conditional OR p || q is "if p then true else q"
}
event.Age)}, nil fmt.Println(err)
! NOT !p is "not p"
} return
switch tag {
}
default: s3()
Variables
func main() {
Switch case 0, 1, 2, 3: s1()
lambda.Start(HandleLambdaEvent) for {
VarDecl = "var" ( VarSpec | "(" { VarSpec ";" } ")" ) .
case 4, 5, 6, 7: s2()
} reader := bufio.NewReader(os.Stdin)
VarSpec = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
}
fmt.Print(">> ")
var i int
text, _ := reader.ReadString('\n')
var U, V, W float64
AWS S3 Bucket List
fmt.Fprintf(c, text+"\n")
Arrays • Slices • Ranges
var k = 0
package main
var x, y float32 = -1, -2
[32]byte
message, _ := bufio.NewReader(c).ReadString('\n')
var (
[2*N] struct { x, y int32 }
import ( fmt.Print("->: " + message)
i int
Arrays [1000]*float64
"fmt" if strings.TrimSpace(string(text)) == "STOP" {
u, v, s = 2.0, 3.0, "bar"
[3][5]int
fmt.Println("TCP client exiting...")
)
[2][2][2]float64 // same as [2]([2]([2]float64))
"github.com/aws/aws-sdk-go/aws" return
var re, im = complexSqrt(-1)
"github.com/aws/aws-sdk-go/aws/session" }
var _, found = entries[name] // map lookup; only interested in "found"
"github.com/aws/aws-sdk-go/service/s3" }
make([]T, length, capacity)
uint8 the set of all unsigned 8-bit integers (0 to 255) ) }
Slices // the following two expressions are equivalent
Create the TCP Server
the set of all unsigned 16-bit integers (0 to 65535) func main() {
uint16 make([]int, 50, 100)
//create a file named tcpS.go
s3svc := s3.New(session.New())
new([100]int)[0:50]
result, err := s3svc.ListBuckets(&s3.ListBucketsInput{})
uint32 the set of all unsigned 32-bit integers (0 to 4294967295)
package main
if err != nil {
// RangeClause = [ ExpressionList "=" | IdentifierList ":=" ]
fmt.Println("Buckets list failed", err)
uint64 the set of all unsigned 64-bit integers (0 to 18446744073709551615)
"range" Expression .
import (
return
"bufio"
}
int8 the set of all signed 8-bit integers (-128 to 127)
var a [10]string
"fmt"
for i, s := range a {
"net"
Ranges
fmt.Println("Buckets:")
int16 // type of i is int
the set of all signed 16-bit integers (-32768 to 32767)
"os"
for _, bucket := range result.Buckets {
// type of s is string
"strings"
fmt.Printf("%s : %s\n", aws.StringValue(bucket.Name),
// s == a[i]
int32 the set of all signed 32-bit integers (-2147483648 to 2147483647)
"time"
bucket.CreationDate)
g(i, s)
)
}
}
the set of all signed 64-bit integers (-9223372036854775808 to
}
int64 9223372036854775807)
func main() {
arguments := os.Args
Test the TCP Client and Server
float32 the set of all IEEE-754 32-bit floating-point numbers
if len(arguments) == 1 {
//Run your TCP server. From the directory containing the tcpS.go file, run the following command: fmt.Println("Please provide port number")
float64 the set of all IEEE-754 64-bit floating-point numbers
return
go run tcpS.go 1234 }
complex64 the set of all complex numbers with float32 real and imaginary parts
//The server will listen on port number 1234. You will not see any output as a result of this command. PORT := ":" + arguments[1]
complex128 //Open a second shell session to execute the TCP client and to interact with the TCP server. Run the following command: l, err := net.Listen("tcp", PORT)
the set of all complex numbers with float64 real and imaginary parts
if err != nil {
go run tcpC.go 127.0.0.1:1234 fmt.Println(err)
byte alias for uint8
return
//Note: If the TCP server is not running on the expected TCP port, you will get the following error message from tcpC.go: }
rune alias for int32
defer l.Close()
dial tcp [::1]:1234: connect: connection refused
Packages
c, err := l.Accept()
// PackageClause = "package" PackageName . //You will see a >> prompt waiting for you to enter some text. Type in Hello! to receive a response from the TCP server: if err != nil {
// PackageName = identifier . fmt.Println(err)
Clause
Hello! return
package math }
//You should see a similar output:
//ImportDecl = "import" ( ImportSpec | "(" { ImportSpec ";" }
for {
")" ) .
>> Hello! netData, err := bufio.NewReader(c).ReadString('\n')
//ImportSpec = [ "." | PackageName ] ImportPath .
->: 2019-05-23T19:43:21+03:00 if err != nil {
//ImportPath = string_lit .
fmt.Println(err)
//Send the STOP command to exit the TCP client and server: return
package main - // Package declaration
}
STOP if strings.TrimSpace(string(netData)) == "STOP" {
// Multiple import statements
fmt.Println("Exiting TCP server!")
Import
import "fmt"
//You should see a similar output in the client: return
import "time"
declarations
}
import "math"
>> STOP
->: TCP client exiting... fmt.Print("-> ", string(netData))
// Factored import statements
t := time.Now()
import (
//The output on the TCP server side will resemble the following: myTime := t.Format(time.RFC3339) + "\n"
"fmt"
c.Write([]byte(myTime))
"time"
-> Hello! }
"math"
Exiting TCP server! }
)
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