[ipsBruno]

pawn Code:

public OnPlayerConnect(playerid)
{
  new string[64], pName[MAX_PLAYER_NAME];
  GetPlayerName(playerid,pName,MAX_PLAYER_NAME);
  format(string,sizeof string,"%s has joined the server. Welcome!",pName);
  SendClientMessageToAll(0xFFFFFFAA,string);
  return 1;
}

e

pawn Code:

public OnPlayerDisconnect(playerid, reason)
{
  new
    string[64],
    name[MAX_PLAYER_NAME];
  GetPlayerName(playerid,name,MAX_PLAYER_NAME);
  switch(reason)
  {
    case 0: format(string,sizeof string,"%s left the server. (Timed out)",name);
    case 1: format(string,sizeof string,"%s left the server. (Leaving)",name);
    case 2: format(string,sizeof string,"%s left the server. (Kicked/Banned)",name);
  }
  SendClientMessageToAll(0xFFFFFFAA,string);
  return 1;
}

by: wiki