simple echo example<\/a> using Gorilla websockets. The echoing example blocks on the sockets until data is available, however that isn’t really going to work here. At first I tried to use the SetReadDeadLine, mirroring non-blocking IO in C. While this worked, it wasn’t really an ideal solution. What I ended up with was my first use of go routines! Basically breaking the code into two threads each of which blocks on reads from the 2 sockets. The code is below for reference (it currently forwards traffic to\/from localhost, but the first 12bytes sent from the client should be the destination host port, I’ll update this post then that codes in place):<\/p>\n\r\npackage main\r\n \r\nimport (\r\n "github.com\/gorilla\/websocket"\r\n "net\/http"\r\n "net"\r\n "fmt"\r\n "io"\r\n)\r\n\r\nvar upgrader = websocket.Upgrader{\r\n ReadBufferSize: 1024,\r\n WriteBufferSize: 1024,\r\n}\r\n\r\n\r\n \r\nfunc print_binary(s []byte) {\r\n fmt.Printf("print b:");\r\n for n := 0;n < len(s);n++ {\r\n fmt.Printf("%d,",s[n]);\r\n }\r\n fmt.Printf("\\n");\r\n}\r\n\r\nfunc address_decode(address_bin []byte) (string,string) {\r\n \r\n var host string = "127.0.0.1"\r\n var port string = "22";\r\n\r\n return host,port\r\n}\r\n \r\n\r\nfunc forwardtcp(wsconn *websocket.Conn,conn net.Conn) {\r\n\r\n for {\r\n \/\/ Receive and forward pending data from tcp socket to web socket\r\n tcpbuffer := make([]byte, 1024)\r\n\r\n n,err := conn.Read(tcpbuffer)\r\n if err == io.EOF { fmt.Printf("TCP Read failed"); break; }\r\n if err == nil {\r\n fmt.Printf("Forwarding from tcp to ws: %d bytes: %s\\n",n,tcpbuffer)\r\n print_binary(tcpbuffer)\r\n wsconn.WriteMessage(websocket.BinaryMessage,tcpbuffer[:n])\r\n }\r\n }\r\n}\r\n\r\nfunc forwardws (wsconn *websocket.Conn,conn net.Conn) {\r\n\r\n for {\r\n \/\/ Send pending data to tcp socket\r\n n,buffer,err := wsconn.ReadMessage()\r\n if err == io.EOF { fmt.Printf("WS Read Failed"); break; }\r\n if err == nil {\r\n s := string(buffer[:len(buffer)])\r\n fmt.Printf("Received (from ws) forwarding to tcp: %d bytes: %s %d\\n",len(buffer),s,n)\r\n print_binary(buffer)\r\n conn.Write(buffer)\r\n }\r\n }\r\n}\r\n\r\nfunc wsProxyHandler(w http.ResponseWriter, r *http.Request) {\r\n\r\n wsconn, err := upgrader.Upgrade(w, r, nil)\r\n\r\n if err != nil {\r\n \/\/log.Println(err)\r\n return\r\n }\r\n\r\n \/\/ get connection address and port\r\n address := make([]byte, 16)\r\n\r\n n,address,err := wsconn.ReadMessage()\r\n if err != nil {\r\n fmt.Printf("address read error");\r\n fmt.Printf("read %d bytes",n); \r\n }\r\n\r\n print_binary(address)\r\n\r\n host, port := address_decode(address)\r\n\r\n conn, err := net.Dial("tcp", host + ":" + port)\r\n if err != nil {\r\n\t\/\/ handle error\r\n }\r\n\r\n go forwardtcp(wsconn,conn)\r\n go forwardws(wsconn,conn)\r\n\r\n fmt.Printf("websocket closed");\r\n}\r\n \r\nfunc main() {\r\n http.HandleFunc("\/echo", wsProxyHandler)\r\n http.Handle("\/", http.FileServer(http.Dir(".")))\r\n err := http.ListenAndServe(":8080", nil)\r\n if err != nil {\r\n panic("Error: " + err.Error())\r\n }\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"I’ve been writing a simple websocket to tcp forwarder in golang for a project I’m working on. I previously showed a simple echo example using Gorilla websockets. The echoing example blocks on the sockets until data is available, however that isn’t really going to work here. At first I tried to use the SetReadDeadLine, mirroring […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1],"tags":[],"class_list":["post-1937","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p1RRoU-vf","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/1937","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/comments?post=1937"}],"version-history":[{"count":1,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/1937\/revisions"}],"predecessor-version":[{"id":1938,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/posts\/1937\/revisions\/1938"}],"wp:attachment":[{"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/media?parent=1937"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/categories?post=1937"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/41j.com\/blog\/wp-json\/wp\/v2\/tags?post=1937"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}