Why the simple Socket Snippet doesn't work?

Sender side:

Code:

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int len = strlen(str);
write(sock,&len,sizeof(int));
write(sock,str,len);

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Receiver Side:

Code:

---

int len;
read(sock,&len,sizeof(int));
char* str=(char*)malloc(len*sizeof(char));
read(sock,str,len);

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what are return values of write and read?
what does it mean - "doesn't work" - how do you check it?

PS. And this is C, why to post on C++ board?

maybe because write() and read() aren't part of the socket API !?

also, what OS? I don't see any of the initialization or setup functions in that snippet. without some more context information it could be anything, a bad pointer, a bad socket, unitialized socket stack, improperly installed drivers, poor feng shui, etc.