#Mumps, 114 115 Bytes

Golfed:

R P F{S J=0,I="|TCP|1" O I:(:P) U I R K F K=1:1:4{S J=J+$P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K)} W J,! C I}

Ungolfed:

R P             ; Read Port # from STDIN ;
  F{            ; Loop over everything;
  S J=0,        ; Initial IP segment total
  I="|TCP|1"    ; TCP device
  O I:(:P)      ; Open the TCP device, port from input {and sticking a tongue out! :-) }
  U I           ; Use the TCP device
  R K           ; Read from STDIN (anything)
  F K=1:1:4{    ; Iterate 1->4 in variable K
    S J=J+      ; Accumulate the following segments of the IP in var. J
    $P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K) ; Grab each piece of IPv4.
            }   ; close the loop.
  W J,!         ; Write the total w/newline out the TCP port 
  C I           ; close the TCP port to send.
}               ; end final loop

This is the InterSystems Caché version of Mumps - if there's a version out there that can acquire the TCP address shorter than ##class(%SYSTEM.TCPDevice).PeerAddr() (as it's almost a 1/3 of the entire program) it might have a better chance against some of the other languages posted already... ;-)

Edit: Thanks to @TimmyD - I missed the reading of the port from STDIN or arguments instead of being hardcoded. Edited; it added 1 byte to the program.

Mumps, 114 115 Bytes

Golfed:

R P F{S J=0,I="|TCP|1" O I:(:P) U I R K F K=1:1:4{S J=J+$P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K)} W J,! C I}

Ungolfed:

R P             ; Read Port # from STDIN ;
  F{            ; Loop over everything;
  S J=0,        ; Initial IP segment total
  I="|TCP|1"    ; TCP device
  O I:(:P)      ; Open the TCP device, port from input {and sticking a tongue out! :-) }
  U I           ; Use the TCP device
  R K           ; Read from STDIN (anything)
  F K=1:1:4{    ; Iterate 1->4 in variable K
    S J=J+      ; Accumulate the following segments of the IP in var. J
    $P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K) ; Grab each piece of IPv4.
            }   ; close the loop.
  W J,!         ; Write the total w/newline out the TCP port 
  C I           ; close the TCP port to send.
}               ; end final loop

This is the InterSystems Caché version of Mumps - if there's a version out there that can acquire the TCP address shorter than ##class(%SYSTEM.TCPDevice).PeerAddr() (as it's almost a 1/3 of the entire program) it might have a better chance against some of the other languages posted already... ;-)

Edit: Thanks to @TimmyD - I missed the reading of the port from STDIN or arguments instead of being hardcoded. Edited; it added 1 byte to the program.

#Mumps, 114 Bytes

Golfed:

F{S J=0,I="|TCP|1" O I:(:1239) U I R K F K=1:1:4{S J=J+$P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K)} W J,! C I}

Ungolfed:

F{              ; Loop over everything;
  S J=0,        ; Initial IP segment total
  I="|TCP|1"    ; TCP device
  O I:(:1239)   ; Open the TCP device, port 1239.
  U I           ; Use the TCP device
  R K           ; Read from STDIN (anything)
  F K=1:1:4{    ; Iterate 1->4 in variable K
    S J=J+      ; Accumulate the following segments of the IP in var. J
    $P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K) ; Grab each piece of IPv4.
            }   ; close the loop.
  W J,!         ; Write the total w/newline out the TCP port 
  C I           ; close the TCP port to send.
}               ; end final loop

This is the InterSystems Caché version of Mumps - if there's a version out there that can acquire the TCP address shorter than ##class(%SYSTEM.TCPDevice).PeerAddr() (as it's almost a 1/3 of the entire program) it might have a better chance against some of the other languages posted already... ;-)

#Mumps, 114 115 Bytes

Golfed:

R P F{S J=0,I="|TCP|1" O I:(:P) U I R K F K=1:1:4{S J=J+$P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K)} W J,! C I}

Ungolfed:

R P             ; Read Port # from STDIN ;
  F{            ; Loop over everything;
  S J=0,        ; Initial IP segment total
  I="|TCP|1"    ; TCP device
  O I:(:P)      ; Open the TCP device, port from input {and sticking a tongue out! :-) }
  U I           ; Use the TCP device
  R K           ; Read from STDIN (anything)
  F K=1:1:4{    ; Iterate 1->4 in variable K
    S J=J+      ; Accumulate the following segments of the IP in var. J
    $P(##class(%SYSTEM.TCPDevice).PeerAddr(),".",K) ; Grab each piece of IPv4.
            }   ; close the loop.
  W J,!         ; Write the total w/newline out the TCP port 
  C I           ; close the TCP port to send.
}               ; end final loop

This is the InterSystems Caché version of Mumps - if there's a version out there that can acquire the TCP address shorter than ##class(%SYSTEM.TCPDevice).PeerAddr() (as it's almost a 1/3 of the entire program) it might have a better chance against some of the other languages posted already... ;-)

Edit: Thanks to @TimmyD - I missed the reading of the port from STDIN or arguments instead of being hardcoded. Edited; it added 1 byte to the program.