C-Socket Programming-"undefined reference" - c

Question

I am a beginner in socket programming in C. I got the code in the book and when I compiled, these are following error with undefined reference. Please give a tips to correct this!Thank you!
Code:
#include <stdio.h>
#include <winsock.h>
#include <winsock2.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define RCVBUFSIZE 32
int main(int argc, char *argv[]){
int sock;
struct sockaddr_in echoServAddr;
unsigned short echoServPort;
char *servIP;
char *echoString;
char echoBuffer[RCVBUFSIZE];
unsigned int echoStringLen;
int bytesRcvd, totalBytesRcvd;
if(argc>3 || argc>4){
printf("Usage: %s <Server IP> <Echo Word> [<Echo Port>\n",argv[0]);
exit(1);
}
servIP=argv[1];
echoString=argv[2];
if(argc==4){
echoServPort=atoi(argv[3]);
}
else{
echoServPort=7;
}
if((sock=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP))<0){
printf("socket() failed!");
}
memset(&echoServAddr,0,sizeof(echoServAddr));
echoServAddr.sin_family=AF_INET;
echoServAddr.sin_addr.s_addr=inet_addr(servIP);
echoServAddr.sin_port=htons(echoServPort);
if (connect(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0){
printf("connect() failed!");
}
echoStringLen=strlen(echoString);
if(send(sock,echoString, echoStringLen,0)!=echoStringLen){
printf("send() send maximum bytes than expected");
}
totalBytesRcvd=0;
printf("Received");
while(totalBytesRcvd<echoStringLen){
if((bytesRcvd=recv(sock,echoBuffer,RCVBUFSIZE-1,0))<=0){
printf("recv() failed!");
}
totalBytesRcvd+=bytesRcvd;
echoBuffer[bytesRcvd]='\0';
printf(echoBuffer);
}
close(sock);
exit(1);
}
I got errors as follow:
In function `main':
client.cpp:34: undefined reference to `_socket#12'
client.cpp:39: undefined reference to `_inet_addr#4'
client.cpp:40: undefined reference to `_htons#4'
client.cpp:41: undefined reference to `_connect#12'
client.cpp:45: undefined reference to `_send#16'
client.cpp:51: undefined reference to `_recv#16'
collect2.exe [Error] ld returned 1 exit status

Answer 1

From my observation, you're trying to build Winsock application with MinGW.
MinGW, by default, don't link Winsock library (which is Ws2_32.lib) automatically, so you need to manually tell compiler by using -l flag plus name of your library.
gcc winsock.c -o winsock.exe -lws2_32
Edit : If you're IDE which are using MinGW suite (Code::Block, DevC++, etc), you can try to find option where you can manually add compiler flags, and add -lws2_32 into on of your compiler flag
Edit : Based on your comment above, so you're using Dev-C++ IDE, below is guide how you can use ws2_32.lib library inside your IDE
Go to top menu Tools, and click Compiler Options...
Inside Compiler Options, tick checkbox Add the following commands when calling the compiler
Put compiler flag -lws2_32 below into the textarea
Press OK
Try again to compile your source code. If nothing go wrong, your program should be compiled successfully.
Regards