C socket - recv: connection reset by peer - c

Question

All is doing fine here, except that the client can't receive the message, or the server can't send it, I don't know.
I have really little time, so I can't waste it anymore trying to handle this problem, so I turn to you guys. Just one thing that I think (maybe) you have to know: the server is under my network, the client is under my school network.
P.S. the different IPs for the server is because I'm behind a NAT, no problem with that.
Client code
const char* IPSERVER = "87.21.70.136";
int main(int argc, char *argv[]){
struct addrinfo hints, *serverInfo;
int s;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version
hints.ai_socktype = SOCK_STREAM;
if(getaddrinfo(IPSERVER, "50", &hints, &serverInfo) != 0){
printf("Errore getaddrinfo(). Chiusura...\n");
exit(-1);
}
s = socket(serverInfo->ai_family, serverInfo->ai_socktype, serverInfo->ai_protocol);
printf("Porta: %d\n", ((struct sockaddr_in * ) serverInfo->ai_addr)->sin_port);
if(connect(s, serverInfo->ai_addr, serverInfo->ai_addrlen) < 0)
perror("Errore connect()");
char buf[2000];
int bytes_rec;
if((bytes_rec = recv(s, buf, sizeof buf, 0)) < 0)
perror("Errore recv");
printf("%s\n",buf);
close(s);
return 0;
}
Server code
struct sockaddr_storage clientAddr;
socklen_t addrSize;
struct addrinfo hints, *myInfo;
int s, newS;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; // use IPv4 or IPv6, whichever
hints.ai_socktype = SOCK_STREAM;
if(getaddrinfo("192.168.1.2", "50", &hints, &myInfo) < 0)
perror("Errore getaddrinfo()");
printf("Porta: %d\n", ((struct sockaddr_in *) myInfo->ai_addr) -> sin_port);
s = socket(myInfo->ai_family, myInfo->ai_socktype, myInfo->ai_protocol);
if(s < 0)
perror("Errore socket()");
printf("Socket stabilita.\n");
if(bind(s, myInfo->ai_addr, myInfo->ai_addrlen) < 0)
perror("Errore bind()");
printf("Porta creata.\n");
if(listen(s, 5) < 0)
perror("Errore listen()");
printf("Server in ascolto...\n");
addrSize = sizeof clientAddr;
if((newS = accept(s, (struct sockaddr * )&clientAddr, &addrSize) < 0))
perror("Errore accept()");
printf("Invio messaggio in corso...\n");
char *msg = "ciao, mi vedi?";
int len, bytes_sent;
len = strlen(msg);
if((bytes_sent = send(newS, msg, len, 0)) < 0)
perror("Errore send()");
printf("Messaggio inviato.\n");
closesocket(newS);
closesocket(s);
WSACleanup();
return 0;
}
Client output
Porta: 12800
Errore recv: Connection reset by peer
Server output
Porta: 12800
Socket stabilita.
Porta creata.
Server in ascolto...
Invio messaggio in corso...
Errore send(): No error
Messaggio inviato.
Process returned 0 (0x0) execution time : 4.789 s
Press any key to continue.

Answer 1

The server code is clearly using the WinSock API, which means the server is running on Windows.
Socket handles on Windows are unsigned values, so int is the wrong data type to use for them. You need to use the SOCKET type instead. And compare the return value of socket() and accept() again the INVALID_SOCKET constant.
Ignoring socket creation errors and passing invalid sockets to send() and recv() can cause them to fail.
perror() operates on errno, which WinSock (and the Win32 API in general) does not use. That would explain the "no error" message after send() fails, because errno is 0. You have to use WSAGetLastError() instead to get a WinSock error code when a WinSock function fails.
With that said, try this server code:
void psocketerror(const char *msg, int err)
{
fprintf(stderr, "%s: %d\n", msg, err);
}
void psocketerror(const char *msg)
{
psocketerror(msg, WSAgetLastError());
}
int main(int argc, char *argv[])
{
struct sockaddr_storage clientAddr;
socklen_t addrSize;
struct addrinfo hints, *myInfo;
SOCKET s, newS;
int err;
WSADATA wsa;
err = WSAStartup(MAKEWORD(2, 0), &wsa);
if (err != 0) {
psocketerror("Errore WSAStartup()", err);
return 1;
}
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
if ((err = getaddrinfo("192.168.1.2", "50", &hints, &myInfo)) < 0) {
psocketerror("Errore getaddrinfo()", err);
WSACleanup();
return 1;
}
printf("Porta: %d\n", ntohs(((struct sockaddr_in *)(myInfo->ai_addr))->sin_port));
s = socket(myInfo->ai_family, myInfo->ai_socktype, myInfo->ai_protocol);
if (s == INVALID_SOCKET) {
psocketerror("Errore socket()");
WSACleanup();
return 1;
}
printf("Socket stabilita.\n");
if (bind(s, myInfo->ai_addr, myInfo->ai_addrlen) < 0) {
psocketerror("Errore bind()");
closesocket(s);
WSACleanup();
return 1;
}
printf("Porta creata.\n");
if (listen(s, 5) < 0) {
psocketerror("Errore listen()");
closesocket(s);
WSACleanup();
return 1;
}
printf("Server in ascolto...\n");
addrSize = sizeof clientAddr;
newS = accept(s, (struct sockaddr * )&clientAddr, &addrSize)
if (newS === INVALID_SOCKET) {
psocketerror("Errore accept()");
closesocket(s);
WSACleanup();
return 1;
}
printf("Invio messaggio in corso...\n");
char *msg = "ciao, mi vedi?";
int len, bytes_sent;
len = strlen(msg);
if ((bytes_sent = send(newS, msg, len, 0)) < 0) {
psocketerror("Errore send()");
closesocket(newS);
closesocket(s);
WSACleanup();
return 1;
}
printf("Messaggio inviato.\n");
closesocket(newS);
closesocket(s);
WSACleanup();
return 0;
}