C submit command to server from client - c

Question

I have a client-server application which runs on UDP ( I need it UDP not tcp ).
A client can send a message to server and it's working fine and vice versa.
I want the client to be able to pass a message as "_connect game1 10" and trigger a function on the server correspondingly which is called _connect(char *name, int num).
How can this be performed to analyse each command to trigger what command ? and is serialisation is a solution and how to implement it.

Answer 1

You can do something on the lines of the following steps
1. Create a message structure
typedef struct info
{
char clientReq[MAX_LENGTH];
char sub[MAX_LENGTH];
u_int32_t value;
u_int16_t end; //Set for the packet which closes the connection
}messageInfo;
On Client
Create socket and bind locally //and connect to server socket(optionally)
fd = socket( family, SOCK_DGRAM, 0 );
//handle error
struct sockaddr_in peerV4;
struct sockaddr_in clientV4;
rc = bind(fd,(struct sockaddr *) &clientV4,
sizeof clientV4);
//error handling
Send the packet data to server.
//update peer(server) socket info here
peerV4.sin_family = AF_INET;
peerV4.sin_port = htons(serverPort);
peerV4.sin_addr.s_addr = "x.x.x.x";
uint8_t *tBuf = (uint8_t *)malloc(sizeof (info)); //memset to zero
info *pHeader = (info *)tBuf;
pHeader->value = htonl(10); //local value to send
pHeader->end = htons(0);
pHeader->clientReq = "connect";
pheader->sub = "game1";
sendto(serverSock, tBuf, sizeof(info),0
,(struct sockaddr *) &peerV4,
sizeof(peerV4));
Send last packet and close local socket.
pHeader->end = htons(1); // so the server closes the socket
//send packet
close(fd);
On Server
1. Create a UDP socket, bind to a local address wait for client to send you the data and use recvfrom
fd = socket( family, SOCK_DGRAM, 0 );
//bind socket
uint8_t *recvBuf = (uint8_t *)malloc(sizeof(info));
info *pheader = (info *)recvBuf;
int currLen = recvfrom( fd, recvBuf,
mBufLen),0,(struct sockaddr *)&peerV4,
&sockaddrLen);
//error handling
if(currLen > 0)
{
if(htons(pheader->end) == 1)
//close socket
char *localSub = pheader->sub;
char *localRecv = pheader->clientReq;
//do something with the values on the server like
if (strcasecmp(localRecv,"connect") == 0) //pseudo
connect(sub,pheader->value)
}