A Simple Makefile
This post presents a simple Makefile that can be used to build 2 programs. Its written to use implicit rules.
Prerequisties
To use this Makefile you need make and GCC. On Ubuntu 16.04.3:
Type sudo apt-get update
Type sudo apt-get install build-essential
Files
Makefile
CFLAGS += -Wall -g
all : \
UDPEchoClient \
UDPEchoServer
UDPEchoClient_objects = \
UDPEchoClient.o \
Practical.o
UDPEchoClient : $(UDPEchoClient_objects)
UDPEchoServer_objects = \
UDPEchoServer.o \
Practical.o
UDPEchoServer : $(UDPEchoServer_objects)
.PHONY : clean all
clean :
rm -f UDPEchoClient $(UDPEchoClient_objects)
rm -f UDPEchoServer $(UDPEchoServer_objects)
UDPEchoClient.c
#include
#include
#include
#include
#include
#include
#include "Practical.h"
int main(int argc, char *argv[]) {
if (argc < 3 || argc > 4)
DieWithUserMessage(
"Parameter(s)",
" [ MAXSTRINGLENGTH)
DieWithUserMessage(echoString, "string too long");
char *servPort = (argc == 4) ? argv[3] : "echo";
struct addrinfo addrCriteria;
memset(&addrCriteria, 0, sizeof(addrCriteria));
addrCriteria.ai_family = AF_UNSPEC;
addrCriteria.ai_socktype = SOCK_DGRAM;
addrCriteria.ai_protocol = IPPROTO_UDP;
struct addrinfo *servAddr;
int rtnVal = getaddrinfo(server, servPort, &addrCriteria, &servAddr);
if (rtnVal != 0)
DieWithUserMessage("getaddrinfo() failed",
gai_strerror(rtnVal));
int sock = socket(servAddr->ai_family, servAddr->ai_socktype,
servAddr->ai_protocol);
if (sock < 0)
DieWithSystemMessage("socket() failed");
ssize_t numBytes = sendto(sock, echoString, echoStringLen, 0,
servAddr->ai_addr, servAddr->ai_addrlen);
if (numBytes < 0)
DieWithSystemMessage("sendto() failed");
else if (numBytes != echoStringLen)
DieWithUserMessage("sendto() error",
"sent unexpected number of bytes");
struct sockaddr_storage fromAddr;
socklen_t fromAddrLen = sizeof(fromAddr);
char buffer[MAXSTRINGLENGTH + 1];
numBytes = recvfrom(sock, buffer, MAXSTRINGLENGTH, 0,
(struct sockaddr *) &fromAddr, &fromAddrLen);
if (numBytes < 0)
DieWithSystemMessage("recvfrom() failed");
else if (numBytes != echoStringLen)
DieWithUserMessage("recvfrom() error",
"received unexpected number of bytes");
if (!SockAddrsEqual(servAddr->ai_addr, (struct sockaddr *) &fromAddr))
DieWithUserMessage("recvfrom()",
"received a packet from unknown source");
freeaddrinfo(servAddr);
buffer[echoStringLen] = '\0';
printf("Received: %s\n", buffer);
close(sock);
exit(0);
}
UDPEchoServer.c
#include
#include
#include
#include
#include
#include
#include "Practical.h"
int main(int argc, char *argv[])
{
if (argc != 2)
DieWithUserMessage("Parameters(s)", "");
char *service = argv[1];
struct addrinfo addrCriteria;
memset(&addrCriteria, 0, sizeof(addrCriteria));
addrCriteria.ai_family = AF_UNSPEC;
addrCriteria.ai_flags = AI_PASSIVE;
addrCriteria.ai_socktype = SOCK_DGRAM;
addrCriteria.ai_protocol = IPPROTO_UDP;
struct addrinfo *servAddr;
int rtnVal = getaddrinfo(NULL, service, &addrCriteria, &servAddr);
if (rtnVal != 0)
DieWithUserMessage("getaddrinfo() failed",
gai_strerror(rtnVal));
int sock = socket(servAddr->ai_family, servAddr->ai_socktype,
servAddr->ai_protocol);
if (sock < 0)
DieWithSystemMessage("socket() failed");
if (bind(sock, servAddr->ai_addr, servAddr->ai_addrlen) < 0)
DieWithSystemMessage("bind() failed");
freeaddrinfo(servAddr);
for (;;) {
struct sockaddr_storage clntAddr;
socklen_t clntAddrLen = sizeof(clntAddr);
char buffer[MAXSTRINGLENGTH];
ssize_t numBytesRcvd = recvfrom(sock,
buffer, MAXSTRINGLENGTH, 0,
(struct sockaddr *) &clntAddr, &clntAddrLen);
if (numBytesRcvd < 0)
DieWithSystemMessage("recvfrom() failed");
fputs("Handling client ", stdout);
PrintSocketAddress((struct sockaddr *) &clntAddr, stdout);
fputc('\n', stdout);
ssize_t numBytesSent = sendto(sock, buffer, numBytesRcvd, 0,
(struct sockaddr *) &clntAddr,
sizeof(clntAddr));
if (numBytesSent < 0)
DieWithSystemMessage("sendto() failed");
else if (numBytesSent != numBytesRcvd)
DieWithUserMessage("sendto()",
"sent unexpected number of bytes");
}
}
Practical.c
#include
#include
#include
#include
#include
#include
void PrintSocketAddress(const struct sockaddr *address, FILE *stream) {
if (address == NULL || stream == NULL)
return;
void *numericAddress;
char addrBuffer[INET6_ADDRSTRLEN];
in_port_t port;
switch (address->sa_family) {
case AF_INET:
numericAddress = &((struct sockaddr_in *) address)->sin_addr;
port = ntohs(((struct sockaddr_in *) address)->sin_port);
break;
case AF_INET6:
numericAddress = &((struct sockaddr_in6 *) address)->sin6_addr;
port = ntohs(((struct sockaddr_in6 *) address)->sin6_port);
break;
default:
fputs("[unknown type]", stream);
return;
}
if (inet_ntop(address->sa_family, numericAddress, addrBuffer,
sizeof(addrBuffer)) == NULL)
fputs("[invalid address]", stream);
else {
fprintf(stream, "%s", addrBuffer);
if (port != 0)
fprintf(stream, "-%u", port);
}
}
int SockAddrsEqual(struct sockaddr *addr1, struct sockaddr *addr2) {
if (addr1 == NULL || addr2 == NULL)
return addr1 == addr2;
else if (addr1->sa_family != addr2->sa_family)
return 0;
else if (addr1->sa_family == AF_INET) {
struct sockaddr_in *ipv4Addr1 = (struct sockaddr_in *) addr1;
struct sockaddr_in *ipv4Addr2 = (struct sockaddr_in *) addr2;
return ipv4Addr1->sin_addr.s_addr == ipv4Addr2->sin_addr.s_addr
&& ipv4Addr1->sin_port == ipv4Addr2->sin_port;
} else if (addr1->sa_family == AF_INET6) {
struct sockaddr_in6 *ipv6Addr1 = (struct sockaddr_in6 *) addr1;
struct sockaddr_in6 *ipv6Addr2 = (struct sockaddr_in6 *) addr2;
return memcmp(&ipv6Addr1->sin6_addr, &ipv6Addr2->sin6_addr,
sizeof(struct in6_addr)) == 0 &&
ipv6Addr1->sin6_port == ipv6Addr2->sin6_port;
} else
return 0;
}
void DieWithUserMessage(const char *msg, const char *detail) {
fputs(msg, stderr);
fputs(": ", stderr);
fputs(detail, stderr);
fputc('\n', stderr);
exit(1);
}
void DieWithSystemMessage(const char *msg) {
perror(msg);
exit(1);
}
Practical.h
#ifndef PRACTICAL_H
#define PRACTICAL_H
#define MAXSTRINGLENGTH 256
void PrintSocketAddress(const struct sockaddr *address, FILE *stream);
int SockAddrsEqual(struct sockaddr *addr1, struct sockaddr *addr2);
void DieWithUserMessage(const char *msg, const char *detail);
void DieWithSystemMessage(const char *msg);
#endif /* PRACTICAL_H */
Usage
Copy everything into one directory
Type make to clean and build everything
Type make all to build everything
Type make clean to clean everything
Run It
Type ./UDPEchoServer 49152 in one terminal
Type ./UDPEchoClient localhost “Hello!” 49152 repeatedly in another terminal
References