diff --git a/nselib/afp.lua b/nselib/afp.lua
index f5ca363d2..2e704ddef 100644
--- a/nselib/afp.lua
+++ b/nselib/afp.lua
@@ -583,9 +583,9 @@ Proto = {
     local new_name = new_name or ""
 
     data = bin.pack(">CCSISI", COMMAND.FPCopyFile, pad, src_vol, src_did, dst_vol, dst_did )
-    data = data .. bin.pack(">CIP", unicode_names, unicode_hint, src_path )
-    data = data .. bin.pack(">CIP", unicode_names, unicode_hint, dst_path )
-    data = data .. bin.pack(">CIP", unicode_names, unicode_hint, new_name )
+    .. bin.pack(">CIP", unicode_names, unicode_hint, src_path )
+    .. bin.pack(">CIP", unicode_names, unicode_hint, dst_path )
+    .. bin.pack(">CIP", unicode_names, unicode_hint, new_name )
 
     packet = self:create_fp_packet( REQUEST.Command, data_offset, data )
     self:send_fp_packet( packet )
@@ -744,39 +744,28 @@ Proto = {
         -- not tested, but should work (next tag is
         -- tested)
         local octet = {}
-        local j
-        local addr
 
         for j = 1, 8 do
-          pos, octet[j] = bin.unpack(">S", packet.data, pos)
+          local o
+          pos, o = bin.unpack(">S", packet.data, pos)
+          octet[j] = string.format("%04x", o)
         end
 
-        for j = 1, 7 do
-          addr = addr .. string.format("%04x:", octet[j])
-        end
-        addr = addr .. string.format("%04x", octet[8])
-
-        table.insert(result.network_addresses, addr)
+        table.insert(result.network_addresses, table.concat(octet, ':'))
       elseif tag == 0x07 then
         -- 16 byte ipv6 and two byte port
         local octet = {}
         local port
-        local j
-        local addr
 
         for j = 1, 8 do
-          pos, octet[j] = bin.unpack(">S", packet.data, pos)
+          local o
+          pos, o = bin.unpack(">S", packet.data, pos)
+          octet[j] = string.format("%04x", o)
         end
         pos, port = bin.unpack(">S", packet.data, pos)
 
-        addr = "["
-
-        for j = 1, 7 do
-          addr = addr .. string.format("%04x:", octet[j])
-        end
-        addr = addr .. string.format("%04x]:%d", octet[8], port)
-
-        table.insert(result.network_addresses, addr)
+        table.insert(result.network_addresses,
+          string.format("[%s]:%d", table.concat(octet, ':'), port))
       end
     end
 
diff --git a/nselib/dhcp.lua b/nselib/dhcp.lua
index 43b6d70e4..b3f943cc2 100644
--- a/nselib/dhcp.lua
+++ b/nselib/dhcp.lua
@@ -20,6 +20,7 @@ local math = require "math"
 local nmap = require "nmap"
 local stdnse = require "stdnse"
 local string = require "string"
+local strbuf = require "strbuf"
 local table = require "table"
 _ENV = stdnse.module("dhcp", stdnse.seeall)
 
@@ -400,7 +401,7 @@ end
 --@return status (true or false)
 --@return The parsed response, as a table.
 function dhcp_build(request_type, ip_address, mac_address, options, request_options, overrides, lease_time, transaction_id)
-  local packet = ''
+  local packet = strbuf.new()
 
   -- Set up the default overrides
   if(overrides == nil) then
@@ -451,7 +452,7 @@ function dhcp_build(request_type, ip_address, mac_address, options, request_opti
 
   packet = packet .. bin.pack(">C", 0xFF)                                                      -- Termination
 
-  return true, packet
+  return true, strbuf.dump(packet)
 end
 
 ---Parse a DHCP packet (either a request or a response) and return the results
diff --git a/nselib/drda.lua b/nselib/drda.lua
index 1d2ffbc99..aa5b403a1 100644
--- a/nselib/drda.lua
+++ b/nselib/drda.lua
@@ -306,11 +306,7 @@ DRDAParameter = {
   --
   -- @return data string containing the DRDA Parameter
   __tostring = function( self )
-    local data = bin.pack(">SS", self.Length, self.CodePoint )
-    if ( self.Data ) then
-      data = data .. bin.pack("A", self.Data)
-    end
-    return data
+    return bin.pack(">SSA", self.Length, self.CodePoint, self.Data or "" )
   end,
 
   --- Builds a DRDA Parameter from a string
diff --git a/nselib/eigrp.lua b/nselib/eigrp.lua
index a8871f4b8..8305937fb 100644
--- a/nselib/eigrp.lua
+++ b/nselib/eigrp.lua
@@ -8,6 +8,7 @@
 local bin = require "bin"
 local table = require "table"
 local stdnse = require "stdnse"
+local strbuf = require "strbuf"
 local ipOps = require "ipOps"
 local packet = require "packet"
 _ENV = stdnse.module("eigrp", stdnse.seeall)
@@ -308,7 +309,8 @@ EIGRP = {
     --- Converts the request to a string suitable to be sent over a socket.
     -- @return data string containing the complete request to send over the socket
     __tostring = function(self)
-      local data = bin.pack(">C", self.ver) -- Version 2
+      local data = strbuf.new()
+      data = data .. bin.pack(">C", self.ver) -- Version 2
       data = data .. bin.pack(">C", self.opcode) -- Opcode: Hello
 
       -- If checksum not manually.
@@ -378,6 +380,7 @@ EIGRP = {
           stdnse.debug1("eigrp.lua: TLV type %d unknown.", tlv.type)
         end
       end
+      data = strbuf.dump(data)
       -- In the end, correct the checksum if not manually set
       if not self.checksum then
         data = data:sub(1,2) .. bin.pack(">S", packet.in_cksum(data)) .. data:sub(5)
diff --git a/nselib/informix.lua b/nselib/informix.lua
index ac9aad6e8..562f5c0a1 100644
--- a/nselib/informix.lua
+++ b/nselib/informix.lua
@@ -722,8 +722,9 @@ Packet.SQ_INFO =
       end
     end
 
-    data = bin.pack(">SSSSS", Constants.Message.SQ_INFO, 0x0006, #params + 6, 0x000c, 0x0004 )
-    data = data .. params .. bin.pack(">SSS", 0x0000, 0x0000, Constants.Message.SQ_EOT)
+    data = bin.pack(">SSSSSASSS", Constants.Message.SQ_INFO, 0x0006,
+      #params + 6, 0x000c, 0x0004, params, 0x0000, 0x0000,
+      Constants.Message.SQ_EOT)
     return data
   end
 }
diff --git a/nselib/jdwp.lua b/nselib/jdwp.lua
index ca0dd9d2e..92a05b08c 100644
--- a/nselib/jdwp.lua
+++ b/nselib/jdwp.lua
@@ -130,20 +130,14 @@ JDWPCommandPacket = {
   -- Packs command packet as a string od bytes, ready to be sent
   -- to the target debuggee.
   pack = function(self)
-    local packed_packet
-    if self.data == nil then
-      packed_packet = bin.pack(">I",11) -- length - minimal header is 11 bytes
-    else
-      packed_packet = bin.pack(">I",11 + #self.data) -- length with data
-    end
-    packed_packet = packed_packet .. bin.pack(">I",self.id)
-    packed_packet = packed_packet .. bin.pack(">C",0) -- flag
-    packed_packet = packed_packet .. bin.pack(">C",self.command_set)
-    packed_packet = packed_packet .. bin.pack(">C",self.command)
-    if self.data then
-      packed_packet = packed_packet .. self.data
-    end
-    return packed_packet
+    local data = self.data or ""
+    return bin.pack(">IICCC",
+      11 + #data, -- length - minimal header is 11 bytes
+      self.id,
+      0, -- flag
+      self.command_set,
+      self.command,
+      data)
   end
 }
 
diff --git a/nselib/ldap.lua b/nselib/ldap.lua
index ae139184a..cdfa68ed3 100644
--- a/nselib/ldap.lua
+++ b/nselib/ldap.lua
@@ -403,8 +403,7 @@ function unbindRequest( socket )
   encoder:registerTagEncoders(tagEncoder)
 
   ldapMessageId = ldapMessageId +1
-  ldapMsg = encode( ldapMessageId )
-  ldapMsg = ldapMsg .. encodeLDAPOp( APPNO.UnbindRequest, false, nil)
+  ldapMsg = encode( ldapMessageId ) .. encodeLDAPOp( APPNO.UnbindRequest, false, nil)
   packet = encoder:encodeSeq( ldapMsg )
   try( socket:send( packet ) )
   return true, ""
diff --git a/nselib/netbios.lua b/nselib/netbios.lua
index f199b33d9..60f8725e2 100644
--- a/nselib/netbios.lua
+++ b/nselib/netbios.lua
@@ -299,9 +299,7 @@ function do_nbstat(host)
   0,       -- Answers
   0,       -- Authority
   0        -- Extra
-  )
-
-  query = query .. bin.pack(">zSS",
+  ) .. bin.pack(">zSS",
   encoded_name, -- Encoded name
   0x0021,       -- Query type (0x21 = NBSTAT)
   0x0001        -- Class = IN
diff --git a/nselib/nrpc.lua b/nselib/nrpc.lua
index 9f0fccdcf..b71bacdcf 100644
--- a/nselib/nrpc.lua
+++ b/nselib/nrpc.lua
@@ -150,8 +150,7 @@ Helper = {
 
     status, data = DominoPacket:new():read( self.domsock )
 
-    id_data = id_data:sub(33)
-    id_data = id_data .. data:sub(11, total_len - #id_data + 11)
+    id_data = id_data:sub(33) .. data:sub(11, total_len - #id_data + 11)
 
     return true, id_data
   end,
diff --git a/nselib/rdp.lua b/nselib/rdp.lua
index 74e7545a2..9d38fda14 100644
--- a/nselib/rdp.lua
+++ b/nselib/rdp.lua
@@ -68,15 +68,19 @@ Packet = {
     end,
 
     __tostring = function(self)
-      local len = (self.code ~= 0xF0 and #self.data + 1 or 2)
-      local data = bin.pack("CC",
-        len,
-        self.code or 0
-      )
-
-      if ( self.code == 0xF0 ) then
-        data = data .. "\x80" -- EOT
+      local len, eot
+      if self.code == 0xF0 then
+        eot = "\x80"
+        len = 2
+      else
+        eot = ""
+        len = #self.data + 1
       end
+      local data = bin.pack("CCA",
+        len,
+        self.code or 0,
+        eot
+      )
 
       return data .. self.data
     end,
diff --git a/nselib/rmi.lua b/nselib/rmi.lua
index 6c09a4a04..08ad3fa5d 100644
--- a/nselib/rmi.lua
+++ b/nselib/rmi.lua
@@ -553,12 +553,11 @@ JavaField = {
   getValue = function( self ) return self.value end,
 
   __tostring = function( self )
-    local data = tostring(self.type) .. " " .. tostring(self.name)
     if self.value ~= nil then
-      data = data .." = " .. tostring(self.value)
+      return string.format("%s %s = %s", self.type, self.name, self.value)
+    else
+      return string.format("%s %s", self.type, self.name)
     end
-
-    return data
   end,
   toTable = function(self)
     local data = {tostring(self.type) .. " " .. tostring(self.name)}
@@ -571,8 +570,7 @@ JavaField = {
           table.insert(data, self.value)
         end
       else
-        --TODO: FIXME This is illegal, but I don't know what the intent was:
-        data = data .." = " .. tostring(self.value) --FIXME
+        table.insert(data, self.value)
       end
     end
     return data
diff --git a/nselib/tftp.lua b/nselib/tftp.lua
index 9a8822f4e..fdab85a89 100644
--- a/nselib/tftp.lua
+++ b/nselib/tftp.lua
@@ -242,19 +242,19 @@ local function processConnection( host, port, data )
     end
   end
 
-  local filecontent = ""
+  local filecontent = {}
 
   -- Make sure we received all the blocks needed to proceed
   for i=1, #blocks do
     if ( not(blocks[i]) ) then
       return false, ("Block #%d was missing in transfer")
     end
-    filecontent = filecontent .. blocks[i]
+    filecontent[#filecontent+1] = blocks[i]
   end
   stdnse.debug1("Finished receiving file \"%s\"", filename)
 
   -- Add  anew file to the global infiles table
-  table.insert( infiles, File:new(filename, filecontent, host) )
+  table.insert( infiles, File:new(filename, table.concat(filecontent), host) )
 
   local condvar = nmap.condvar(infiles)
   condvar "broadcast"
diff --git a/nselib/vulns.lua b/nselib/vulns.lua
index 0a5ca9e65..859e8efb2 100644
--- a/nselib/vulns.lua
+++ b/nselib/vulns.lua
@@ -689,9 +689,8 @@ local l_update_id = function(fid_table, id_type, id, vuln_table)
   local push_table = fid_table[id_type][id]['ENTRIES']
 
   if vuln_table.host and next(vuln_table.host) then
-    local host_info = string_format(" (host:%s", vuln_table.host.ip)
     local target_key = l_get_host_port_key(vuln_table)
-    host_info = host_info..string_format(" %s)", target_key)
+    local host_info = string_format(" (host:%s %s)", vuln_table.host.ip, target_key)
 
     debug(5,
       "vulns.lua: Updating VULNS.FILTERS_IDS{} with '%s' ID:%s:%s %s",
@@ -1006,10 +1005,8 @@ local l_add = function(vulndb, vuln_table)
 
   local host_info, target_key = "", ""
   if vuln_table.host and next(vuln_table.host) then
-    host_info = string_format(" (host:%s", vuln_table.host.ip)
-
     target_key = l_get_host_port_key(vuln_table)
-    host_info = host_info..string_format(" %s)", target_key)
+    host_info = string_format(" (host:%s %s)", vuln_table.host.ip, target_key)
   end
 
   -- Search the Filters IDS for the vulnerability
@@ -1817,18 +1814,16 @@ local format_vuln_base = function(vuln_table, showall)
       string_format("  State: %s", STATE_MSG[vuln_table.state]))
 
   if vuln_table.IDS and next(vuln_table.IDS) then
-    local ids_str = ""
     local ids_t = {}
     for id_type, id in pairs(vuln_table.IDS) do
       -- ignore internal NMAP IDs
       if id_type ~= 'NMAP_ID' then
-        ids_str = ids_str .. string_format("  %s:%s", id_type, id)
         table.insert(ids_t, string_format("%s:%s", id_type, id))
       end
     end
 
-    if ids_str:len() > 0 then
-      insert(out, string_format("  IDs:%s", ids_str))
+    if next(ids_t) then
+      insert(out, string_format("  IDs:  %s", table.concat(ids_t, "  ")))
       output_table.ids = ids_t
     end
   end
@@ -1852,10 +1847,8 @@ local format_vuln_base = function(vuln_table, showall)
     if vuln_table.description then
       local desc = format_vuln_special_fields(vuln_table.description)
       if desc then
-        local desc_str = ""
         for _, line in ipairs(desc) do
           insert(out, string_format("    %s", line))
-          desc_str = desc_str .. line
         end
         output_table.description = vuln_table.description
       end