tcpconnect: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/tcpconnect - from package: tcputils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/tcpconnect - from package: tcputils

You may install the required package with command apt-get install {package}

Error in other languages:
tcpconnect: bevel nie gevind nie
tcpconnect: comandă negăsită
tcpconnect: comando não encontrado
tcpconnect: commande introuvable
tcpconnect: command not found
tcpconnect: käsku ei ole
tcpconnect: không tìm thấy lệnh
tcpconnect: komanda nerasta
tcpconnect: Kommando nicht gefunden.
tcpconnect: kommandot finns inte
tcpconnect: komut yok
tcpconnect: nie znaleziono polecenia
tcpconnect: níor aimsíodh an t-ordú
tcpconnect: no se encontró la orden
tcpconnect: no s'ha trobat l'ordre
tcpconnect: opdracht niet gevonden
tcpconnect: parancs nem található
tcpconnect: perintah tidak ditemukan
tcpconnect: príkaz nenájdený
tcpconnect: příkaz nenalezen
tcpconnect: команда не найдена
tcpconnect: командата не е открита
tcpconnect: 命令找不到
tcpconnect: コマンドが見つかりません