3 way UDP chat program segmentation fault

I am having some difficulty with this program. Right now I am running into a segmentation fault whenever anything is sent to the server. I also need to create a database to store those that enter the chat so that private messages can be sent to them but I have no idea how I should go about doing that. I believe the client is 99% of the way done, I just need to uncomment the one line (sending username to server for database). The server is where I am having difficulty I believe. I will provide the code.

Client

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>

extern int errno;

int main (int argc, char *argv[]){
	char hname[255];
	struct sockaddr_in sin;
	struct sockaddr_in lin;
	socklen_t sinlength;
	socklen_t linlength;
	struct hostent *ph;
	int thesock;
	int len;
	long address;
	char host[40];
	char strinput[4096];
	char strinput2[4096];
	char buf[4096];
	char x;
	struct sockaddr_in to_addr;
	struct sockaddr_in from;
	socklen_t fromlen;
	int i;
	char username[20];
	int pid;
	char message;
	int s;

	
	if (argc != 3){
		printf("Usage:   ./a.out 172.21.24.1 port\n");
		exit(1);
	}
	else{
		strcpy(host, argv[1]);
	}
	
	if ((ph = gethostbyname (host)) == NULL){
		switch (h_errno){
			case HOST_NOT_FOUND:
				fprintf(stderr, "%s: no such host %s\n", argv[0], host);
				exit(1);
			case TRY_AGAIN:
				fprintf(stderr, "%s: host %s, try again later\n", argv[0], host);
				exit(1);
			case NO_RECOVERY:
				fprintf(stderr, "%s: host %s   DNS ERROR\n", argv[0], host);
				exit(1);
			case NO_ADDRESS:
				fprintf(stderr, "%s: No IP address for %s\n", argv[0], host);
				exit(1);
			default:
				fprintf(stderr, "Unknown error: %d\n", h_errno);
				exit(1);
			}
		}
	else {
		memcpy ((char *) &sin.sin_addr, (char *) ph ->h_addr, ph -> h_length);
		sin.sin_family = PF_INET;
	}
	
	i = gethostname(host, len);

	sin.sin_port = atoi(argv[2]);
	
	if ((s = socket (PF_INET, SOCK_DGRAM, 0)) < 0) {
		perror ("socket");
		exit(1);
	}
	
	lin.sin_family = PF_INET;
	lin.sin_addr.s_addr = INADDR_ANY;
	lin.sin_port = 0;

	linlength = sizeof(lin);
	
	if (bind(s, (struct sockaddr *) &lin, linlength) < 0){
		perror ("bind");
		exit(1);
	}
	
	if (getsockname(s, (struct sockaddr *) &lin, (socklen_t *) &linlength) < 0){
		perror ("getsockname");
		exit(1);
	}
	
	printf("What is your username?\n");
	fgets(username, 20, stdin);
	
	len = sizeof(hname);
	sinlength = sizeof(struct sockaddr_in);
//	sendto(s, username, strlen(username), 0, (struct sockaddr *) &sin, sizeof (struct sockaddr));
	
	printf("\n");
	printf("You can send any text that you want. There are 2 special commands.\n");
	printf(".send <username> = send a private message to the username specified.\n");
	printf("(DO NOT INCLUDE <> IN THE COMMAND\n");
	printf(".quit = quit the program.\n");
	printf("\n");

	while(1){
		pid = fork();
		if (pid==0){
			recvfrom(s, buf, 4095, 0, (struct sockaddr *) &from, &fromlen);
			buf[message] = '\0';
			printf("\n(%s, %d) said : ", inet_ntoa(from.sin_addr), ntohs(from.sin_port));
			printf("%s", buf);
			printf("\n");
			printf("\n");
		}
		else {
			char * strinput2;
			fgets(strinput, 4095, stdin);
			if (strinput2 = strstr (strinput, ".quit")){
				sendto(s, strinput2, strlen(strinput2), 0, (struct sockaddr *) &sin, sizeof (struct sockaddr));
				recvfrom(s, buf, 4095, 0, (struct sockaddr *) &from, &fromlen);
				printf("The Client is now closing.\n");
				close(s);
				while ('\n' != getchar()){
					getchar();
					exit(1);
				}
			}
			else{
				sendto(s, strinput, strlen(strinput), 0, (struct sockaddr *) &sin, sizeof (struct sockaddr));
			}
		}
	}
}

Server

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>

extern int errno;

int main(int argc, char *argv[]){
	const char * message;
	int i;
	int s;
	int fd;
	int len;
	struct sockaddr_in sin;
	int sinlength;
	char buf[BUFSIZ];
	int buflen;
	char x;
	char strinput[50];
	struct sockaddr_in from;
	socklen_t fromlen;

	int action;

	if ((s = socket(PF_INET, SOCK_DGRAM,0)) < 0){
		perror("Socket");
		exit(1);
	}
	sin.sin_family = PF_INET;
	sin.sin_addr.s_addr = INADDR_ANY;
	sin.sin_port = 0;
	sinlength = sizeof(sin);

	if (bind(s, (struct sockaddr *) &sin, sinlength) < 0){
		perror("bind");
		exit(1);
	}
	
	if (getsockname(s, (struct sockaddr *) &sin, (socklen_t *) &sinlength) < 0){
		perror("getsockname");
		exit(1);
	}

	printf ("Socket is using port %d\n", sin.sin_port);
	printf ("The Server is now running.\n");

	while(1){
		recvfrom(s, buf, buflen, 0, (struct sockaddr *) &from, &fromlen);
//		buf[message] = '\0';
		message==buf;
		if (message = strstr(message, ".quit")){
			char *reply;
			reply = "Acknowledged Quit command";
			printf ("(%s , %d) has left the forum");
			sendto(s, reply, strlen(reply), 0, (struct sockaddr *) &from, fromlen);
			close(s);
			while ('\n' != getchar()){
				getchar();
				exit(1);
			}
		}
		if (message = strstr(message, ".send")){
			//parse .send
				//parse username
					sendto(s, message, strlen(message), 0, (struct sockaddr *) &from, fromlen);
		}
		else {
			printf("(%s , %d) said : ", inet_ntoa(from.sin_addr), ntohs(from.sin_port));
			sendto(s, message, strlen(message), 0, (struct sockaddr *) &from, fromlen);
		}
	}
}

Any help will be greatly appreciated. I have been working on this program for 3 weeks now and it is driving me crazy. I have never used C before only C++ and I have never done any socket programming. I also am not good with linux so if there are any commands you suggest me to use please explain them fully.